fix: Add depends_on to Eventarc trigger

[NimJay]

• Please see Google-internal bug: b/372430497#comment27
• In that bug, we encountered the following error during terraform destroy:

Error: Error deleting Trigger: operation received error: error code "7", message: 
An internal error occurred.
...
To use GCS CloudEvent triggers, the GCS service account requires the Pub/Sub Publisher (roles/pubsub.publisher) IAM role in the specified project. 1 

• I believe it's because the role (roles/pubsub.publisher) on the GCS (Google Cloud Storage) service account
• The fix is to ensures the Eventarc trigger is deleted before the GCS service account's role (roles/pubsub.publisher).

[github-actions]

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