Merge pull request #15303 from MicrosoftDocs/herohua-patch-1

remove the unused legacy MSDN template from publishing config

Author: herohua

.openpublishing.publish.config.json

@@ -41,12 +41,6 @@
       "branch": "master",
       "branch_mapping": {}
     },
-    {
-      "path_to_root": "_themes.MSDN.Modern",
-      "url": "https://github.com/Microsoft/templates.msdn.msft",
-      "branch": "master",
-      "branch_mapping": {}
-    },
     {
       "path_to_root": "samples",
       "url": "https://github.com/dotnet/samples",