ci: Update macOS image

The macOS 12 GHA image has been deprecated since 2024-10-07.
See: https://github.com/actions/runner-images/issues/10721

.github/workflows/ci.yml

@@ -680,10 +680,10 @@ jobs:
         run: env
         if: ${{ always() }}
 
-  macos-native:
-    name: "x86_64: macOS Monterey"
+  x86_64-macos-native:
+    name: "x86_64: macOS Ventura, Valgrind"
     # See: https://github.com/actions/runner-images#available-images.
-    runs-on: macos-12 # Use M1 once available https://github.com/github/roadmap/issues/528
+    runs-on: macos-13
 
     env:
       CC: 'clang'