chore: enable `usetesting` linter #3666

Job	Run time
ensure_snapshots_are_being_cleaned	5s
prettier	6s
golangci-lint	32s
prepare_test_image_fixtures	2m 29s
Run unit tests (ubuntu-latest)	1m 51s
Run unit tests (macos-latest)	3m 54s
Run unit tests (windows-latest)	6m 19s
	15m 16s

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