Remove macOS CI runner (GPU not available in VMs)

Metal GPU tests require a physical GPU which GitHub Actions
macos-14 runners don't provide (VMs without GPU access).
Metal tests will run locally only.

Author: Sébastien Loisel

.github/workflows/CI.yml

@@ -49,42 +49,6 @@ jobs:
         with:
           files: lcov.info
           token: ${{ secrets.CODECOV_TOKEN }}
-          flags: ubuntu
-          fail_ci_if_error: false
-
-  test-macos:
-    name: Test (macOS/Metal)
-    runs-on: macos-14  # Apple Silicon with Metal GPU support
-    timeout-minutes: 60
-    steps:
-      - uses: actions/checkout@v4
-
-      - name: Install MPI
-        run: brew install mpich
-
-      - uses: julia-actions/setup-julia@v2
-        with:
-          version: '1.10'
-
-      - uses: julia-actions/cache@v2
-
-      - name: Build package
-        uses: julia-actions/julia-buildpkg@v1
-
-      - name: Run tests with coverage
-        uses: julia-actions/julia-runtest@v1
-        with:
-          coverage: true
-
-      - name: Process coverage
-        uses: julia-actions/julia-processcoverage@v1
-
-      - name: Upload coverage to Codecov
-        uses: codecov/codecov-action@v4
-        with:
-          files: lcov.info
-          token: ${{ secrets.CODECOV_TOKEN }}
-          flags: macos-metal
           fail_ci_if_error: false
 
   docs: