Switch Azure Pipelines iOS image (#2563)

* Revert Azure iOS runners to macos-14.

* Add warning about known macos-15 issues on Github Actions and Azure.

* Update workflow reference with actual ticket.

.github/workflows/test.yml

@@ -76,7 +76,7 @@ jobs:
         - os: macos-13
           python_version: '3.13'
           test_select: ios
-        - os: macos-14  # 20250811 macos-15 update caused havoc with iOS simulators
+        - os: macos-14  # See https://github.com/actions/runner-images/issues/12777
           python_version: '3.13'
           test_select: ios
         - os: macos-13