Remove MinGW 32-bit CI (#434)

* CI: Enable automatic Mirror Updates for MSYS2 and bump libobjc2 rt version

* Remove MinGW 32-bit CI and pin runtime version at 2.0

.github/workflows/main.yml

@@ -181,14 +181,6 @@ jobs:
  fail-fast: false
  matrix:
  include:
- - name: Windows x86 MinGW GCC
- allow-test-failures: true
- arch: i686
- msystem: MINGW32
- library-combo: gnu-gnu-gnu
- CC: gcc
- CXX: g++
-
  - name: Windows x64 MinGW GCC
  arch: x86_64
  msystem: MINGW64
@@ -283,6 +275,7 @@ jobs:
  if: env.CC == 'gcc'
  with:
  msystem: ${{ matrix.msystem }}
+ update: true
  install: >
  mingw-w64-${{matrix.arch}}-gcc-objc