docs: bots to app terminological changes

CONTRIBUTING.md

@@ -22,13 +22,13 @@ We'd also love PRs. If you're thinking of a large PR, we advise opening up an is
 
 Use [this search][good-first-issue-search] to find Probot apps that have issues marked with the `good-first-issue` label.
 
-## Bots
+## Apps
 
-We have one bot enabled on this repo:
+We have one app enabled on this repo:
 
 - [Stale](https://probot.github.io/apps/stale/): We use Stale (the app created in this repo) to ensure that conversations here remain relevant. This is for us, the maintainers, so that we don't feel like we've got hundreds of issues to deal with; if you still have an issue, please let us know! We don't want to close issues that are painful for you. Stale just helps us have a bit more breathing space by making sure issues don't pile up forever.
 
-If you're concerned about our bots or feel that they are insensitive in some way, please let us know.
+If you're concerned about our apps or feel that they are insensitive in some way, please let us know.
 
 ## Resources