chore(deps): bump rxdart from 0.27.7 to 0.28.0 in /packages/stream_chat

Bumps [rxdart](https://github.com/ReactiveX/rxdart) from 0.27.7 to 0.28.0.
- [Release notes](https://github.com/ReactiveX/rxdart/releases)
- [Commits](ReactiveX/rxdart@0.27.7...0.28.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

packages/stream_chat/pubspec.yaml

@@ -21,7 +21,7 @@ dependencies:
   meta: ^1.9.1
   mime: ^1.0.5
   rate_limiter: ^1.0.0
-  rxdart: ^0.27.7
+  rxdart: ">=0.27.7 <0.29.0"
   synchronized: ^3.1.0+1
   uuid: ^4.4.0
   web_socket_channel: ^2.4.5