Fix faulty validation of subtask names in sequence tasks #1175

Job	Run time
Check coding standards	40s
Run tests (Ubuntu, 3.8)	1m 49s
Run tests (Ubuntu, 3.9)	1m 35s
Run tests (Ubuntu, 3.10)	1m 35s
Run tests (Ubuntu, 3.11)	1m 37s
Run tests (Ubuntu, 3.12)	1m 39s
Run tests (MacOS, 3.8)	1m 55s
Run tests (MacOS, 3.9)	1m 48s
Run tests (MacOS, 3.10)	1m 26s
Run tests (MacOS, 3.11)	1m 12s
Run tests (MacOS, 3.12)	1m 12s
Run tests (Windows, 3.9)	2m 49s
Run tests (Windows, 3.10)	2m 56s
Run tests (Windows, 3.11)	2m 51s
Run tests (Windows, 3.12)	2m 47s
Build distribution	9s
Upload release to PyPI	0s
Sign the Python 🐍 distribution 📦 with Sigstore and upload them to GitHub Release	0s
Upload homebrew formula	0s
	28m 0s

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