MAINT switch to macOS 12 on Azure Pipelines (scikit-learn#29281)

Author: ogrisel

azure-pipelines.yml

@@ -247,7 +247,7 @@ jobs:
 - template: build_tools/azure/posix.yml
   parameters:
     name: macOS
-    vmImage: macOS-11
+    vmImage: macOS-12
     dependsOn: [linting, git_commit, Ubuntu_Jammy_Jellyfish]
     # Runs when dependencies succeeded or skipped
     condition: |