Disable MIPS in CI. (#793) #3315

Job	Run time
Check nightly-only targets (nightly)	29s
Check selected Tier 3 platforms (nightly)	3m 6s
Check (stable)	3m 55s
Check --no-default-features (nightly)	1m 18s
Check (nightly)	3m 53s
Rustfmt	9s
Check (1.48)	4m 54s
Test rustix_use_experimental_asm (powerpc64le-linux)	1m 2s
Test use-libc (ubuntu)	53s
Test (ubuntu)	3m 25s
Test use-libc (i686-linux)	1m 3s
Test (ubuntu-20.04)	53s
Test use-libc (aarch64-linux)	1m 13s
Test (i686-linux)	1m 11s
Test use-libc (powerpc64le-linux)	57s
Test (aarch64-linux)	1m 17s
Test use-libc (riscv64-linux)	54s
Test (powerpc64le-linux)	1m 15s
Test use-libc (arm-linux)	1m 9s
Test (riscv64-linux)	1m 16s
Test (s390x-linux)	2m 44s
Test (arm-linux)	3m 1s
Test (ubuntu-stable)	57s
Test (ubuntu-1.48)	3m 48s
Test (i686-linux-stable)	1m 6s
Test (aarch64-linux-stable)	1m 4s
Test (riscv64-linux-stable)	1m 19s
Test (s390x-linux-stable)	2m 32s
Test (powerpc64le-linux-stable)	1m 4s
Test (arm-linux-stable)	2m 50s
Test (ubuntu-1.48)	3m 39s
Test (i686-linux-1.48)	3m 34s
Test (aarch64-linux-1.48)	3m 33s
Test (riscv64-linux-1.48)	3m 35s
Test (s390x-linux-1.48)	3m 52s
Test (powerpc64le-linux-1.48)	3m 49s
Test (arm-linux-1.48)	3m 51s
Test (macos-latest)	1m 3s
Test (macos-11)	52s
Test (windows)	3m 35s
Test (windows-2019)	3m 35s
	1h 29m 35s

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