remove outdated links at bottom of README (#2400)

*Replace this paragraph with a description of what this PR is changing
or adding, and why. Consider including before/after screenshots.*

*List which issues are fixed by this PR. For larger changes, raising an
issue first helps
reduce redundant work.*

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [ ] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-devrel
channel on [Discord].

<!-- Links -->
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Style-guide-for-Flutter-repo.md
[CLA]: https://cla.developers.google.com/
[Discord]:
https://github.com/flutter/flutter/blob/master/docs/contributing/Chat.md
[Contributors Guide]:
https://github.com/flutter/samples/blob/main/CONTRIBUTING.md

Author: sethladd

add_to_app/README.md

@@ -51,14 +51,7 @@ module](https://docs.flutter.dev/add-to-app/debugging). This will
 allow you to hot reload, set breakpoints, and use DevTools and other debugging
 functionality, similar to a full Flutter app.
 
-## Questions/issues
-
-If you have a general question about incorporating Flutter into an existing
-iOS or Android app, the best places to go are:
-
-* [The FlutterDev Google Group](https://groups.google.com/forum/#!forum/flutter-dev)
-* [The Flutter Gitter channel](https://gitter.im/flutter/flutter)
-* [StackOverflow](https://stackoverflow.com/questions/tagged/flutter)
+## Issues
 
 If you run into an issue with the sample itself, please file an issue
 in the [main Flutter repo](https://github.com/flutter/flutter/issues).