Remove double setting of _is_running #3375

Job	Run time
Cache identify	4s
Shellcheck	6s
Dependency	5s
Prepare	8s
Ruff check and force	10s
Check commit	31s
Run pytest using Python 3.14	34s
Process test coverage	13s
Run mypy	0s
Process test complexity	8s
Build and publish Python 🐍 distributions 📦 to TestPyPI	15s
	2m 14s

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