Condense docstring for UnresolvedMarkerWarning #1324

Job	Run time
Run tests (3.8)	1m 42s
Run tests with different pydantic versions	3m 27s
Run tests with coverage	2m 52s
Run tests (3.12)	1m 56s
Run tests (3.9)	1m 44s
Run linters (pydocstyle)	1m 36s
Run tests (3.10)	1m 50s
Run linters (flake8)	1m 29s
Run tests (3.11)	1m 48s
Run tests (3.13)	1m 59s
Run linters (mypy)	1m 38s
Run linters (pylint)	1m 38s
	23m 39s

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