Enable mypy for tests #1755

Job	Run time
mypy	12s
ruff-sort-imports	6s
ruff-check	3s
pyiron / commit-updated-env	5s
pyiron / test-alternate-env	1m 20s
pyiron / benchmark-tests	1m 0s
pyiron / build-notebooks	1m 27s
pyiron / black	9s
pyiron / build-docs	1m 29s
pyiron / pip-check	1m 6s
pyiron / unit-tests (ubuntu-22.04, 3.12)	1m 15s
pyiron / unit-tests (ubuntu-22.04, 3.11)	1m 16s
pyiron / unit-tests (ubuntu-22.04, 3.10)	1m 20s
pyiron / unit-tests (windows-latest, 3.12)	1m 14s
pyiron / unit-tests (macos-latest, 3.12)	1m 19s
pyiron / coveralls-and-codacy / Tests-and-Coverage	1m 39s
	15m 0s

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