PYTHON-5772 Increase _gcp_helpers.py coverage #9155

Job	Run time
DocTest	1m 0s
Test minimum dependencies and Python	49s
Docs Checks	41s
Coverage	12m 25s
Typing Tests (3.10)	1m 3s
static	2m 56s
CPython pypy-3.11-ubuntu-latest	12m 37s
Typing Tests (3.11)	58s
CPython 3.13t-ubuntu-latest	11m 23s
Link Check	3m 37s
Make an sdist	20s
CPython 3.10-ubuntu-latest	11m 38s
Integration Tests	53s
Install from SDist and Test	1m 3s
	1h 1m 23s

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