Add a note about re generating Gradle lockfiles (#55150)

Adds a note that Gradle lockfile generation is necessary when updating the android embedding dependencies bundle.

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: gmackall

tools/cipd/android_embedding_bundle/README.md

@@ -34,3 +34,11 @@ below explain how to fetch the license information for the dependencies.
    new tag: `last_updated:"$version_tag"`.
 1. Update the GN list `embedding_dependencies_jars` in
    `src/flutter/shell/platform/android/BUILD.gn`.
+
+## Updating Gradle Lockfiles in the Framework After Adding Dependencies
+If you land a pr that changes the versions of the embedding dependencies,
+or adds a new dependency and makes use of it, you will also need to
+perform a manual roll of that change to the framework that re-generates
+the Gradle lockfiles using the script at
+`<framework_repo>/dev/tools/bin/generate_gradle_lockfiles.dart`
+(run with the `--no-gradle-generation` and `--no-exclusion` flags).