workflow: Update macOS-11 to macOS-12 runner

.github/workflows/ci.yml

@@ -6,7 +6,7 @@ jobs:
     if: "!contains(github.event.head_commit.message, '[skip ci]') && !contains(github.event.head_commit.message, '[ci skip]')"
     strategy:
       matrix:
-        os: [ubuntu-20.04, windows-2019, macOS-11]
+        os: [ubuntu-20.04, windows-2019, macOS-12]
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v1