Stop using the latest workflow from google-cloud-java

The latest was an experiment to confirm the hermetic build
generation workflow in the previous release cycle.

Author: suztomo

.github/workflows/hermetic_library_generation.yaml

@@ -40,7 +40,6 @@ jobs:
     - uses: googleapis/google-cloud-java/sdk-platform-java/.github/scripts@google-cloud-shared-dependencies/v3.61.0
       if: env.SHOULD_RUN == 'true'
       with:
-        image_tag: latest
         base_ref: ${{ github.base_ref }}
         head_ref: ${{ github.head_ref }}
         token: ${{ secrets.CLOUD_JAVA_BOT_GITHUB_TOKEN }}