Fix conda-based CI

Author: traversaro

.github/workflows/conda-ci.yml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       matrix:
         build_type: [Release]
-        os: [ubuntu-latest, windows-2019, macOS-latest]
+        os: [ubuntu-latest, windows-2019, macos-12]
       fail-fast: false
 
     steps: