Update service name in desc (Azure#18110)

Co-authored-by: Jinghua Zhu <[email protected]>

Author: 2 people

specification/dashboard/resource-manager/Microsoft.Dashboard/preview/2021-09-01-preview/grafana.json

@@ -717,7 +717,7 @@
     "WorkspaceNameParameter": {
       "in": "path",
       "name": "workspaceName",
-      "description": "The name of Azure Managed Workspace for Grafana.",
+      "description": "The name of Azure Managed Grafana.",
       "required": true,
       "type": "string",
       "x-ms-parameter-location": "method"