chore: simplify checklists in pull request template (#9713)

Many PRs end up without completed checklists. This updates the checklist
to a single item for the both the author and reviewer.

Even though we lose in granularity in the checklist, I think this is
only a theoretical regression as I rarely see partially-completed
checklists (and when I do, they rarely come with a comment explaining
why which makes it impossible to know if it was an intentional
omission).

## Checklist

- [x] The PR description includes an overview of the change
- [x] The PR description articulates the motivation for the change
- [x] The change includes tests OR the PR description describes a
testing strategy
- [x] The PR description notes risks associated with the change, if any
- [x] Newly-added code is easy to change
- [x] The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- [x] The change includes or references documentation updates if
necessary
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [x] Title is accurate
- [x] All changes are related to the pull request's stated goal
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- [x] Testing strategy adequately addresses listed risks
- [x] Newly-added code is easy to change
- [x] Release note makes sense to a user of the library
- [x] If necessary, author has acknowledged and discussed the
performance implications of this PR as reported in the benchmarks PR
comment
- [x] Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Co-authored-by: Emmett Butler <[email protected]>

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,21 +1,21 @@
 ## Checklist
-
-- [ ] The PR description includes an overview of the change
-- [ ] The PR description articulates the motivation for the change
-- [ ] The change includes tests OR the PR description describes a testing strategy
-- [ ] The PR description notes risks associated with the change, if any
-- [ ] Newly-added code is easy to change
-- [ ] The change follows the [library release note guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
-- [ ] The change includes or references documentation updates if necessary
-- [ ] Backport labels are set (if [applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))
+- [ ] PR author has checked that all the criteria below are met
+- The PR description includes an overview of the change
+- The PR description articulates the motivation for the change
+- The change includes tests OR the PR description describes a testing strategy
+- The PR description notes risks associated with the change, if any
+- Newly-added code is easy to change
+- The change follows the [library release note guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
+- The change includes or references documentation updates if necessary
+- Backport labels are set (if [applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))
 
 ## Reviewer Checklist
-
-- [ ] Title is accurate
-- [ ] All changes are related to the pull request's stated goal
-- [ ] Avoids breaking [API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces) changes
-- [ ] Testing strategy adequately addresses listed risks
-- [ ] Newly-added code is easy to change
-- [ ] Release note makes sense to a user of the library
-- [ ] If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
-- [ ] Backport labels are set in a manner that is consistent with the [release branch maintenance policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)
+- [ ] Reviewer has checked that all the criteria below are met 
+- Title is accurate
+- All changes are related to the pull request's stated goal
+- Avoids breaking [API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces) changes
+- Testing strategy adequately addresses listed risks
+- Newly-added code is easy to change
+- Release note makes sense to a user of the library
+- If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment
+- Backport labels are set in a manner that is consistent with the [release branch maintenance policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)