Remove need to use `tempfile` #91

Job	Run time
validation (ubuntu-latest, stable)	11s
validation (ubuntu-latest, beta)	23s
validation (macos-latest, stable)	1m 1s
validation (macos-latest, beta)	56s
validation (windows-latest, stable)	2m 3s
validation (windows-latest, beta)	1m 17s
	5m 51s

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