`CircularTupleWindows` does not need phantom data #614

Job	Run time
test	55s
check format	11s
check	12s
check (--no-default-features)	13s
check (--no-default-features --features use_alloc)	14s
msrv	1m 18s
check (--all-targets --all-features)	22s
All checks succeeded	1s
	3m 26s

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