[roll] Update external/github.com/flutter/flutter

external/github.com/flutter/flutter 9313285..5b4a5da (1 commits)
5b4a5da Revert "[O] Fix a race condition in vmservice_test.dart" (#23647)

Test: CQ

Change-Id: I8eb05a9a4ba95929d38160b1057c9287de3edddd
1 file changed