Remove msys from CI and install fypp via msys2 package

.github/workflows/ci_windows.yml

@@ -13,7 +13,6 @@ jobs:
       fail-fast: false
       matrix:
         include: [
-          { msystem: MSYS,    arch: x86_64 },
           { msystem: MINGW64, arch: x86_64 },
           { msystem: MINGW32, arch: i686   }
         ]
@@ -25,7 +24,6 @@ jobs:
 
     - name: Setup MinGW native environment
       uses: msys2/setup-msys2@v2
-      if: contains(matrix.msystem, 'MINGW')
       with:
         msystem: ${{ matrix.msystem }}
         update: false
@@ -34,29 +32,10 @@ jobs:
           mingw-w64-${{ matrix.arch }}-gcc
           mingw-w64-${{ matrix.arch }}-gcc-fortran
           mingw-w64-${{ matrix.arch }}-python
-          mingw-w64-${{ matrix.arch }}-python-pip
-          mingw-w64-${{ matrix.arch }}-python-setuptools
+          mingw-w64-${{ matrix.arch }}-python-fypp
           mingw-w64-${{ matrix.arch }}-cmake
           mingw-w64-${{ matrix.arch }}-ninja
 
-    - name: Setup msys POSIX environment
-      uses: msys2/setup-msys2@v2
-      if: contains(matrix.msystem, 'MSYS')
-      with:
-        msystem: MSYS
-        update: false
-        install: >-
-          git
-          mingw-w64-x86_64-gcc
-          mingw-w64-x86_64-gcc-fortran
-          python
-          python-pip
-          cmake
-          ninja
-
-    - name: Install fypp
-      run: pip install fypp
-
     - run: >-
         PATH=$PATH:/mingw64/bin/ cmake
         -Wdev