ci: pin trio for starlette (#8058) [backport 1.20] (#8073)

starlette framework `starlette-testsuite-0_17_1` is failing due to trio
last release 0.24.0
Pin trio version to avoid errors.

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [x] Title is accurate.
- [x] No unnecessary changes are introduced.
- [x] Description motivates each change.
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Testing strategy adequately addresses listed risk(s).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] Release note makes sense to a user of the library.
- [x] Reviewer has explicitly 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)
- [x] If this PR touches code that signs or publishes builds or
packages, or handles credentials of any kind, I've requested a review
from `@DataDog/security-design-and-guidance`.
- [x] This PR doesn't touch any of that.

(cherry picked from commit 7683e60)

Co-authored-by: Christophe Papazian <[email protected]>

Author: gnufede

.github/workflows/test_frameworks.yml

@@ -442,6 +442,10 @@ jobs:
       - name: Pin urllib3
         if: needs.needs-run.outputs.outcome == 'success'
         run: pip install urllib3==1.26.15
+      # with trio 0.24.0 we are seeing AttributeErrors, pinning while investigating root issue.
+      - name: Pin trio
+        if: needs.needs-run.outputs.outcome == 'success'
+        run: pip install trio==0.23.2
       #Parameters for keyword expression skip 3 failing tests that are expected due to asserting on headers. The errors are because our context propagation headers are being added
       #test_staticfiles_with_invalid_dir_permissions_returns_401 fails with and without ddtrace enabled
       - name: Run tests