Update GitHub Actions macos runner to 13.

Author: mitchell-as

.github/workflows/build.yml

@@ -39,7 +39,7 @@ jobs:
           - 1.22.x
         sys:
           - {os: ubuntu-latest}
-          - {os: macos-12, shell: zsh}
+          - {os: macos-13, shell: zsh}
           - {os: windows-2019}
       fail-fast: false
     runs-on: ${{ matrix.sys.os }}