feat: re-enable flutter_rfb

[Goddchen]

Since I have merged this PR that removes the obsolete lint rules: Goddchen/flutter-rfb#24

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read the Flutter Style Guide recently, and have followed its advice.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

[parlough]

Thanks for landing the fixes and updating this!

[auto-submit]

auto label is removed for flutter/tests/428, due to This PR has not met approval requirements for merging. The PR author is not a member of flutter-hackers and needs 1 more review(s) in order to merge this PR.

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[srawlins]

Thanks!