ci: use CLOUD_JAVA_BOT_GITHUB_TOKEN

The old secret has been deleted. Let's use the new one.

b/509523021

Author: suztomo

.github/workflows/hermetic_library_generation.yaml

@@ -43,4 +43,4 @@ jobs:
         image_tag: latest
         base_ref: ${{ github.base_ref }}
         head_ref: ${{ github.head_ref }}
-        token: ${{ secrets.CLOUD_JAVA_BOT_TOKEN }}
+        token: ${{ secrets.CLOUD_JAVA_BOT_GITHUB_TOKEN }}