Reenable RISC-V Zk and Zb `assert_instr` #1812

Job	Run time
Check Style	17s
Env Override	32s
Test (i686-unknown-linux-gnu)	2m 58s
Build std_detect	1m 52s
Build Documentation	1m 33s
Test (x86_64-unknown-linux-gnu)	8m 36s
Automatic intrinsic verification	48s
Test (x86_64-unknown-linux-gnu-emulated)	12m 12s
Test (arm-unknown-linux-gnueabihf)	3m 9s
Test (armv7-unknown-linux-gnueabihf)	17m 11s
Test (aarch64-unknown-linux-gnu)	40m 16s
Test (riscv64gc-unknown-linux-gnu)	2m 28s
Test (powerpc64le-unknown-linux-gnu)	7m 10s
Test (s390x-unknown-linux-gnu)	2m 54s
Test (wasm32-wasi)	3m 6s
Test (i586-unknown-linux-gnu)	3m 40s
Test (nvptx64-nvidia-cuda)	49s
Test (thumbv6m-none-eabi)	19s
Test (thumbv7m-none-eabi)	17s
Test (thumbv7em-none-eabi)	22s
Test (thumbv7em-none-eabihf)	19s
Test (aarch64-apple-darwin)	1m 51s
Test (x86_64-pc-windows-msvc)	10m 9s
Test (i686-pc-windows-msvc)	4m 51s
Test (x86_64-apple-darwin, macos-11)	7m 53s
	2h 15m 32s

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