run CI on macos-12

Author: zbjornson

.github/workflows/ci.yaml

@@ -58,7 +58,7 @@ jobs:
 
   macOS:
     name: Test on macOS
-    runs-on: macos-latest
+    runs-on: macos-12
     strategy:
       matrix:
         node: [18.12.0, 20.9.0]