Bump flutter_riverpod from 2.2.0 to 2.3.4

Bumps [flutter_riverpod](https://github.com/rrousselGit/riverpod) from 2.2.0 to 2.3.4.
- [Release notes](https://github.com/rrousselGit/riverpod/releases)
- [Commits](rrousselGit/riverpod@flutter_riverpod-v2.2.0...flutter_riverpod-v2.3.4)

---
updated-dependencies:
- dependency-name: flutter_riverpod
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>