message: clarify register management group operation
diff: "Providers"
  ],
  "operationId": "Providers_RegisterAtManagementGroupScope",
  - "description": "Registers a management group with a resource provider.",
  + "description": "Registers a management group with a resource provider. Use this operation to register a resource provider with resource types that can be deployed at the management group scope. It does not recursively register subscriptions within the management group. Instead, you must register subscriptions individually.",
  "parameters": [
  {
  "name": "resourceProviderNamespace",
  