Bump anyio[curio,trio] in /testing/plugins_integration
Bumps [anyio[curio,trio]](https://github.com/agronholm/anyio) from 3.0.1 to 3.1.0.
- [Release notes](https://github.com/agronholm/anyio/releases)
- [Changelog](https://github.com/agronholm/anyio/blob/master/docs/versionhistory.rst)
- [Commits](https://github.com/agronholm/anyio/compare/3.0.1...3.1.0)
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