[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
diff --git a/manifest/flutter b/manifest/flutter
index 7e5ea8f..2a53648 100644
--- a/manifest/flutter
+++ b/manifest/flutter
@@ -4,7 +4,7 @@
     <project name="external/github.com/flutter/flutter"
              path="third_party/dart-pkg/git/flutter"
              remote="https://chromium.googlesource.com/external/github.com/flutter/flutter"
-             revision="931328596ac48a848953f330a192fc33425a378a"/>
+             revision="5b4a5da78edd15aba5dbb0e3711361c5d00c8b6d"/>
     <project name="external/github.com/flutter/engine"
              path="third_party/flutter"
              remote="https://chromium.googlesource.com/external/github.com/flutter/engine"