chore: Update PR template to mention API changes

.github/pull_request_template.md

@@ -2,21 +2,20 @@
 
 <!-- A summary of what this pull request achieves and a rough list of changes. -->
 
-## Breaking Changes
+## API Changes
 
-<!-- Optional, if there are any breaking changes document them, including how to migrate older code. -->
+<!-- Optional, any API additions, deprecations or breaking changes, including how to migrate older code. -->
 
 ## Notes & open questions
 
-<!-- Any notes, remarks or open questions you have to make about the -->
-<!-- PR. -->
+<!-- Any notes, remarks or open questions you have to make about the PR. -->
 
 ## Change checklist
-<!-- Remove any that are not relevant. -->
+
 - [ ] Self-review.
 - [ ] Documentation updates following the [style guide](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#appendix-a-full-conventions-text), if relevant.
 - [ ] Tests if relevant.
-- [ ] All breaking changes documented.
+- [ ] All API changes documented.
 - [ ] This PR was created by a human that thought critically about the
       proposed change and wrote an as clear and concise description as
       they could.