.github/workflows/config.yml: use intel MacOS

Author: k-okada

.github/workflows/config.yml

@@ -153,7 +153,7 @@ jobs:
 
 
   osx:
-    runs-on: macos-latest
+    runs-on: macos-13  # https://github.com/actions/runner-images/blob/main/images/macos/macos-13-Readme.md
     timeout-minutes: 60
     steps:
       - name: Checkout