[gardening] Update 3xHEAD apply script.

It is currently failing because it is trying to cd in non-existent directory.

Change-Id: I29f3947db6aa0e34d747309b310da565dc0c010d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/103137
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
Commit-Queue: Vyacheslav Egorov <vegorov@google.com>
Auto-Submit: Vyacheslav Egorov <vegorov@google.com>
diff --git a/tools/patches/flutter-engine/apply.sh b/tools/patches/flutter-engine/apply.sh
index 9c2bd33..06811d4 100755
--- a/tools/patches/flutter-engine/apply.sh
+++ b/tools/patches/flutter-engine/apply.sh
@@ -53,7 +53,7 @@
   # DEPS file might have been patched with new version of packages that
   # Dart SDK depends on. Get information about dependencies from the
   # DEPS file and forcefully update checkouts of those dependencies.
-  gclient.py revinfo | grep 'src/third_party/dart/' | while read -r line; do
+  gclient.py revinfo | grep 'src/third_party/dart/third_party' | while read -r line; do
     # revinfo would produce lines in the following format:
     #     path: git-url@tag-or-hash
     # Where no spaces occur inside path, git-url or tag-or-hash.