Added global ms.date to docfx.json, so that API docs show a respectab… (#123)

dotnet/docfx.json

@@ -56,8 +56,8 @@
       "apiPlatform": "dotnet",
       "author": "natke",
       "ms.author": "nakersha",
+      "ms.date": "11/08/2019",
       "uhfHeaderId": "MSDocsHeader-DotNet",
-      "apiPlatform": "dotnet",
       "searchScope": [".NET"],
       "ms.topic": "managed-reference",
       "ms.prod": "dotnet-ml-api",