[sdk-platform-java] [Hermetic Build] update_generation_config.yaml action fails if the existing config update PR has merge conflicts

https://github.com/googleapis/java-pubsublite/pull/1879 was not being updated for several days:

This is because https://github.com/googleapis/java-pubsublite/pull/1879 had merge conflicts

In this cycle, I have observed this in 5 repositories including this one