chore: updates PR template

[latin-panda]

What has been done to verify that this works as intended?

Why is this the best possible solution? Were any other approaches considered?

• Removes checks that are already covered by automation (e.g., CI failures and merge blocking)
• Simplify the long question while still conveying the same meaning
• Adds warning to remind contributors to branch off next, so it's more visible

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

Does this change require updates to documentation? If so, please file an issue here and include the link below.

Before submitting this PR, please make sure you have:

• branched off and targeted the next branch OR only changed documentation/infrastructure (master is stable and used in production)
• verified that any code or assets from external sources are properly credited in comments or that everything is internally sourced

[latin-panda]

@lognaturel, If this looks good, I'll update the other central repositories as well.