[changelog] Add implements-Function breaking change to the changelog
[changelog] Add implements-Function breaking change to the changelog

Change-Id: I32a4800a73861922040e3f9b1130b702fafa1d56
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/143332
Reviewed-by: Johnni Winther <0f64ef784d57ffb064b634040f9eeba0d33d0be4@google.com>
Commit-Queue: Sigmund Cherem <beaea8fd7d2a56555046ba4f362c8a93e3938576@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk