Reland: Always use new plugin schema for plugin template (#49832)

Now that the new schema is supported on the stable channel, and the old
schema is considered legacy, the template should always create plugins
using the new schema.
https://dart.googlesource.com/external/github.com/flutter/flutter/+/33bb1faf5bd08f4cc13146b8b05c34978ea8482e
diff --git a/commits.json b/commits.json
index 3b0273b..97963bf 100644
--- a/commits.json
+++ b/commits.json
@@ -1,5 +1,5 @@
 {
   "external/github.com/flutter/engine":"7a25baedad542484d8b16af2c6ae8582d60546fa",
-  "external/github.com/flutter/flutter":"9de7787f258870e60a7c4127883e8f7f1af5822c",
+  "external/github.com/flutter/flutter":"33bb1faf5bd08f4cc13146b8b05c34978ea8482e",
   "sdk":"c790e0c4017d54457021a5a4636a43858a617183"
 }
\ No newline at end of file