Update docfx.json

Added uhfHeaderId value per build report.

Author: chrisda

whiteboard/docfx.json

@@ -54,6 +54,7 @@
     "overwrite": [],
     "externalReference": [],
     "globalMetadata": {
+      "uhfHeaderId": "MSDocsHeader-M365-IT",
       "author" : "tbrosman",
       "ms.author" : "tbrosman",
       "manager" : "shanejc",