Bump `rand` for direct-minimal-versions compat. #307

Job	Run time
build (ubuntu, stable, locked, true)	6m 13s
no_std	36s
build (windows, stable, locked, false)	5m 55s
miri	1m 50s
build (macos, stable, locked, false)	6m 12s
build (ubuntu, nightly, locked, false)	6m 11s
build (ubuntu, beta, locked, false)	6m 12s
build (ubuntu, stable, latest, false)	6m 12s
build (ubuntu, stable, minimal, false)	2m 41s
deploy	1s
features	1s
fuzz	1s
	42m 5s

Provide feedback