chore: update sdk-platform-java-nightly.yaml link to action (googleapis#12218)

Follow-up to googleapis#12212, missed one occurrence. Update the url to failed job
after "nightly" job, the corresponding to "nightly-java8" is updated in
googleapis#12212.

For googleapis#12206

Author: zhumin8

.github/workflows/sdk-platform-java-nightly.yaml

@@ -48,7 +48,7 @@ jobs:
         run: |
           gh issue create \
             --title "Nightly build for Java ${{ matrix.java }} on ${{ matrix.os }} failed." \
-            --body "The build has failed : https://github.com/googleapis/gapic-generator-java/actions/runs/${GITHUB_RUN_ID}"
+            --body "The build has failed : https://github.com/googleapis/google-cloud-java/actions/runs/${GITHUB_RUN_ID}"
   nightly-java8: # Compile with JDK 11. Run tests with JDK 8.
     needs: filter
     if: ${{ needs.filter.outputs.library == 'true' }}