Interpret naive datetimes as UTC #1691

Job	Run time
dev and docs requirements check	23s
docs	1m 54s
min-versions	13s
build (3.9, ubuntu-latest)	1m 6s
pre-release	15s
upstream	0s
build (3.9, windows-latest)	1m 49s
build (3.10, ubuntu-latest)	1m 31s
build (3.10, windows-latest)	1m 48s
build (3.10, macos-latest)	1m 12s
build (3.11, ubuntu-latest)	56s
build (3.11, windows-latest)	1m 48s
build (3.11, macos-latest)	50s
build (3.12, ubuntu-latest)	1m 3s
build (3.12, windows-latest)	1m 48s
build (3.12, macos-latest)	51s
	17m 27s

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