Revert "macos-latest now refers to macOS 14 runner"

This reverts commit 0a93f3147c9404f56114ef2e77e6333b594e7358.

.github/workflows/ci.yml

@@ -6,7 +6,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, windows-latest, macos-latest, macos-13]
+        os: [ubuntu-latest, windows-latest, macos-latest, macos-14]
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4