ci: use macos-13 instead of macos-12

macos-12 will be unavailable soon.

Author: kou

.github/workflows/ci.yml

@@ -13,7 +13,7 @@ jobs:
       fail-fast: false
       matrix:
         os:
-          - macos-12
+          - macos-13
           - macos-14
           - ubuntu-latest
           - windows-latest