Merge pull request #44 from JuliaMath/vs/ci

Update CI.yml to insist macOS 12.

Author: ViralBShah

.github/workflows/CI.yml

@@ -17,7 +17,7 @@ jobs:
           - 'nightly'
         os:
 #          - ubuntu-latest
-          - macOS-latest
+          - macOS-12
 #          - windows-latest
         arch:
           - x64