CI: trying out macos 14 image (which is arm64).

Author: devnexen

.github/workflows/full_ci.yml

@@ -221,6 +221,7 @@ jobs:
           - { toolchain: beta, os: macos-13 }
           - { toolchain: nightly, os: macos-13 }
           - { toolchain: 1.71.0, os: macos-13 }
+          - { toolchain: nightly, os: macos-14 }
     runs-on: ${{ matrix.target.os }}
     steps:
       - uses: actions/checkout@v4