Remove mips support

See rust-lang/rust#115218

.github/workflows/ci.yml

@@ -27,12 +27,7 @@ jobs:
         # targets of 'stable' and 'beta' for good measure.
         - pinned
         - stable
-        # Our release builds are generated by a nightly compiler to take
-        # advantage of the latest optimizations/compile time improvements. So
-        # we test all of them here. (We don't do mips releases, but test on
-        # mips for big-endian coverage.)
         - musl
-        - mips
         - arm
         - macos
         - win-msvc
@@ -48,10 +43,6 @@ jobs:
           os: ubuntu-22.04
           rust: stable
           target: x86_64-unknown-linux-musl
-        - build: mips
-          os: ubuntu-22.04
-          rust: stable
-          target: mips64-unknown-linux-gnuabi64
         - build: arm
           os: ubuntu-22.04
           rust: stable