Bump MSRV to 1.63 #15

Job	Run time
Cross (sparcv9-sun-solaris)	27s
Cross (x86_64-unknown-illumos)	30s
Cross (x86_64-unknown-freebsd)	29s
Cross (x86_64-unknown-netbsd)	51s
Apple Other	1m 37s
Tier 2 (x86_64-unknown-fuchsia)	12s
Tier 3 (x86_64-unknown-hermit)	24s
Tier 2 (x86_64-unknown-redox)	17s
Tier 3 (x86_64-wrs-vxworks)	24s
Tier 2 (x86_64-fortanix-unknown-sgx)	12s
Tier 3 (aarch64-kmc-solid_asp3)	23s
Tier 3 (armv6k-nintendo-3ds)	21s
Tier 3 (armv7-sony-vita-newlibeabihf)	28s
Wasm64	35s
Tier 3 (aarch64-unknown-nto-qnx710)	32s
Tier 3 (x86_64-unknown-openbsd, std)	32s
Tier 3 (x86_64-unknown-dragonfly, std)	31s
Tier 3 (x86_64-unknown-haiku, std)	31s
Tier 3 (i686-unknown-hurd-gnu, std)	37s
ESP-IDF	22s
RDRAND (x86_64-unknown-uefi)	23s
No Atomics	25s
RDRAND (x86_64-unknown-l4re-uclibc)	27s
RNDR	23s
	11m 53s

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