use latest image tag

Author: suztomo

.github/workflows/hermetic_library_generation.yaml

@@ -40,6 +40,7 @@ jobs:
     - uses: googleapis/google-cloud-java/sdk-platform-java/.github/scripts@v1.85.0
       if: env.SHOULD_RUN == 'true'
       with:
+        image_tag: latest
         base_ref: ${{ github.base_ref }}
         head_ref: ${{ github.head_ref }}
         token: ${{ secrets.CLOUD_JAVA_BOT_TOKEN }}