Disable MIPS in CI. (#793) #3316

Job	Run time
Check nightly-only targets (nightly)	31s
Check --no-default-features (nightly)	1m 15s
Check selected Tier 3 platforms (nightly)	3m 13s
Check (stable)	6m 48s
Rustfmt	6s
Check (nightly)	3m 49s
Test rustix_use_experimental_asm (powerpc64le-linux)	1m 21s
Check (1.48)	11m 55s
Test use-libc (ubuntu)	35s
Test (ubuntu)	47s
Test use-libc (i686-linux)	1m 14s
Test (ubuntu-20.04)	1m 6s
Test use-libc (aarch64-linux)	1m 3s
Test (i686-linux)	1m 22s
Test use-libc (powerpc64le-linux)	1m 2s
Test (aarch64-linux)	1m 20s
Test (powerpc64le-linux)	1m 14s
Test use-libc (riscv64-linux)	56s
Test (riscv64-linux)	1m 26s
Test use-libc (arm-linux)	1m 2s
Test (s390x-linux)	1m 43s
Test (arm-linux)	1m 12s
Test (ubuntu-stable)	49s
Test (ubuntu-1.48)	4m 15s
Test (i686-linux-stable)	1m 7s
Test (aarch64-linux-stable)	1m 10s
Test (riscv64-linux-stable)	1m 20s
Test (s390x-linux-stable)	1m 16s
Test (powerpc64le-linux-stable)	1m 32s
Test (arm-linux-stable)	3m 38s
Test (ubuntu-1.48)	4m 31s
Test (i686-linux-1.48)	5m 29s
Test (aarch64-linux-1.48)	5m 30s
Test (riscv64-linux-1.48)	5m 35s
Test (s390x-linux-1.48)	6m 16s
Test (powerpc64le-linux-1.48)	4m 57s
Test (arm-linux-1.48)	5m 39s
Test (macos-latest)	55s
Test (macos-11)	51s
Test (windows)	6h 0m 1s
Test (windows-2019)	6h 0m 1s
	13h 39m 52s

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