base32ct+base64ct: unpin `proptest`; MSRV 1.65 #2291

Job	Run time
build (1.65.0, thumbv7em-none-eabi)	55s
build (1.65.0, wasm32-unknown-unknown)	53s
test (1.65.0)	1m 15s
build (stable, thumbv7em-none-eabi)	21s
test (stable)	28s
build (stable, wasm32-unknown-unknown)	21s
minimal-versions / minimal-versions	1m 4s
	5m 17s

Provide feedback