message: add x-ms-enum for orbital
diff: "EarthObservation",
  "Communication"
  ],
  + "x-ms-enum": {
  + "name": "CapabilityType",
  + "modelAsString": true
  + },
  "default": "EarthObservation",
  "description": "Ground Station Capability",
  "x-ms-parameter-location": "method"
  