Don't encourage or require first-time contributors to sign the PCA before submitting a pull request (#1838)

Our friendly `mr.roboto` bot nags them to do so. And our docs warn them that we may ignore or close PRs for people who don't bother to read and follow our guidelines.

Also clean up some wording and grammar.

Author: stevepiercy

docs/contributing/first-time.md

@@ -67,8 +67,7 @@ Such motivation behind these contributions usually results in poor quality break
 ## Requirements
 
 All first-time contributors to Plone must follow the contributing requirements described in {doc}`index`.
-**Do this step now.**
-If you skip this step, then your contribution can't be accepted.
+Although you can open a pull request at any time, Plone Team members may ignore it until, or close it unless, you satisfy the contributing requirements.
 
 For [Plone Google Summer of Code (GSoC)](https://plone.org/community/gsoc) applicants, you must also follow both our and its program guidelines.
 
@@ -80,10 +79,6 @@ For [Plone Google Summer of Code (GSoC)](https://plone.org/community/gsoc) appli
 Contributions to Plone are managed through git repositories on GitHub.
 This section first discusses what not to do, then how to work effectively with a project on GitHub.
 
-```{danger}
-Only people who have completed the {ref}`first-time-requirements-label` described above should make contributions.
-```
-
 
 (things-not-to-do-label)=
 
@@ -95,8 +90,8 @@ Learn from their mistakes, and don't commit them yourself.
 (mistake-1-label)=
 
 1.  **Never ask to be assigned to an issue.**
-    If an issue is unclaimed—either by assignment, an open pull request, or an explicit comment such as "I am working on this issue"—then it is available to work on by **any member of a Plone Team in GitHub**.
-    As a member of a Plone Team, you may post a comment in any unclaimed issue to claim it.
+    If an issue is claimed—either by assignment, an open pull request, or an explicit comment such as "I am working on this issue"—then it is not available to work on.
+    Otherwise, it is available, and you must claim it before you start work on it.
     See {ref}`Avoid duplicate effort <mistake-2-label>`.
     Privileged Plone Team members may ignore or delete comments asking to be assigned to an issue.
 
@@ -116,7 +111,7 @@ Learn from their mistakes, and don't commit them yourself.
     You should instead learn how to {ref}`work-with-github-issues-label` and {ref}`run tests and code quality checks locally <test-and-code-quality-label>`.
 
 4.  **Don't ask if an issue is open.**
-    Instead you can determine whether an issue is open by doing your own research using the following tips.
+    Instead, you can determine whether an issue is open by doing your own research using the following tips.
 
     -   Start Plone or its specific package, follow the steps to attempt to reproduce the issue, and see if it still exists.
     -   Check the issue's status indicator for a green label of {guilabel}`Open`.
@@ -142,11 +137,11 @@ New contributors should wait for an invitation to join this team, and accept it,
 
 ### `mr-roboto` on GitHub
 
-[`mr-roboto`](https://github.com/plone/mr.roboto) enforces the requirement of a signed Plone Contributor Agreement from a new contributor, and being assigned to a Plone team on GitHub.
+[`mr-roboto`](https://github.com/plone/mr.roboto) enforces the requirement of a signed Plone Contributor Agreement from all contributors by virtue of being assigned to a Plone Team on GitHub.
 
-New contributors to Plone who submit a pull request and do not wait for confirmation that they have been added to the Contributors team will be subjected to persistent nagging from `mr-roboto`.
-`mr-roboto` will not respond to you if you `@` it.
-Core developers may ignore your contribution because you did not follow these instructions.
+New contributors to Plone who submit a pull request and do not wait for confirmation that they have been added to the Contributors Team will be subjected to persistent nagging from `mr-roboto`.
+`mr-roboto` will not respond to you if you `@` it, and if you do that anyway, then that indicates you did not read these guidelines.
+Plone Team members may ignore or close your contribution because you did not follow these instructions.
 Please don't be "that person".
 
 
@@ -183,7 +178,7 @@ After you have satisfied the above steps and have clear direction on how to proc
 
 As a member of the Plone Contributors Team, you do not have write access to push commits to GitHub repositories under the Plone organization.
 You can push commits to your fork.
-Thus a typical workflow will be circular in nature.
+Thus, a typical workflow will be circular in nature.
 You will pull code from the upstream Plone repository, push your work from your local clone to your remote fork, then make a pull request from your fork to the upstream Plone repository.
 
 ````{card}

docs/contributing/index.md

@@ -34,7 +34,7 @@ A volunteer member of the Plone Foundation will review your signed agreement.
 If accepted, your GitHub account will be added to a team in the Plone GitHub organization with appropriate access, and you will simultaneously receive an email from GitHub for you to accept the invitation to join the team.
 
 Allow up to one week for processing.
-Contact the Plone Foundation by its email address for further information, including the status of your request.
+Contact the Plone Foundation at [email protected] for further information, including the status of your request.
 
 ```{button-link} https://plone.org/foundation/contributors-agreement
 :color: primary