build(deps): Bump anyio[trio] in /testing/plugins_integration (#13303)

Bumps [anyio[trio]](https://github.com/agronholm/anyio) from 4.8.0 to 4.9.0.
- [Release notes](https://github.com/agronholm/anyio/releases)
- [Changelog](https://github.com/agronholm/anyio/blob/master/docs/versionhistory.rst)
- [Commits](agronholm/anyio@4.8.0...4.9.0)

---
updated-dependencies:
- dependency-name: anyio[trio]
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

testing/plugins_integration/requirements.txt

@@ -1,4 +1,4 @@
-anyio[trio]==4.8.0
+anyio[trio]==4.9.0
 django==5.1.7
 pytest-asyncio==0.25.3
 pytest-bdd==8.1.0