Bump the msrv to 1.65.0 to allow for upgrading hashbrown #55

Job	Run time
cross_test (stable, i686-unknown-linux-gnu)	1m 40s
test (5555)	4s
format (stable)	9s
cross_test (stable, s390x-unknown-linux-gnu)	1m 50s
test (nightly)	11s
coverage (nightly)	1m 1s
test (stable)	18s
test (beta)	13s
	5m 26s

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