ci: Move Type of Change from PR template to CONTRIBUTING (#6522)

Now that prefixes in PR titles are being validated as part of CI, the "Type of Change" section in the PR template is no longer needed. The prefixes and descriptions in the `CONTRIBUTING.md` file have been updated to reflect the currently supported list.

.github/pull_request_template.md

@@ -29,22 +29,6 @@ If a refactor, how is this better than the previous implementation?
 If there is a spec or design document for this feature, please link it here.
 -->
 
-### Type of Change
-
-<!--
-Please check [x] relevant options, delete irrelevant ones.
--->
-
-- [ ] Bug fix (non-breaking change which fixes an issue)
-- [ ] New feature (non-breaking change which adds functionality)
-- [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
-- [ ] Refactor (non-breaking change that only restructures code)
-- [ ] Performance (increase or change in throughput and/or latency)
-- [ ] Tests (you added tests for code that already exists, or your new feature included in this PR)
-- [ ] Documentation update
-- [ ] Chore (no impact to binary, e.g. `.gitignore`, formatting, dropping support for older tooling)
-- [ ] Release
-
 ### API Impact
 
 <!--