Change flutter patch to match existing DEPS on master branch

Change-Id: Idb0fd43ed680839f24e8be03e6703e3be31b8802
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/155445
Reviewed-by: Jonas Termansen <sortie@google.com>

Author: whesse

tools/patches/flutter-engine/a3815b659047cfc6b63d41d180aa1ca1b781ee68.patch

@@ -6,8 +6,7 @@ index 01113f340..e55da1cff 100644
    # Dart is: https://github.com/dart-lang/sdk/blob/master/DEPS.
    # You can use //tools/dart/create_updated_flutter_deps.py to produce
    # updated revision list of existing dependencies.
--  'dart_revision': '84e5eeaea43ec1d636c8742b55c1bc0527b436c8',
-+  'dart_revision': '9b79101c2e8db6875b62ed2ad5042df74f8d0fe1',
+   'dart_revision': 'a3815b659047cfc6b63d41d180aa1ca1b781ee68',
 
    # WARNING: DO NOT EDIT MANUALLY
    # The lines between blank lines above and below are generated by a script. See create_updated_flutter_deps.py