Merge pull request #530 from ComputationalCryoEM/update_azure_osx15

Roll stable MacOS tests to 10.15 from 10.14

Author: garrettwrong

azure-pipelines.yml

@@ -86,9 +86,9 @@ jobs:
     displayName: pytest
 
 - job:
-  displayName: macOS-10.14
+  displayName: macOS-10.15
   pool:
-    vmImage: 'macOS-10.14'
+    vmImage: 'macOS-10.15'
   strategy:
     matrix:
       Python36: