Fix Cloud Build trigger name and teardown method

[bhirsz]

Our internal CI can produce longer ENV_ID - which would make the trigger name too long. Removed "test" from the name to shorten the trigger name.

Also added a missing teardown method for the trigger.

[ashb]

This appears to have broken the docs build

 WARNING: duplicate object description of tests.system.providers.google.cloud.cloud_build.example_cloud_build_trigger.TRIGGER_NAME, other instance in 
_api/tests/system/providers/google/cloud/cloud_build/example_cloud_build_trigger/index, use :noindex: for one of them

File path: apache-airflow-providers-google/_api/tests/system/providers/google/cloud/cloud_build/example_cloud_build_trigger/index.rst (42)

Edit: ah or a PR race with #27783

[potiuk]

ah or a PR race with #27783

Yep. Looks like race between the two indeed.