[ReleasePR dashboard] Rename GrafanaResource as ManagedGrfana (#2257)

Create to sync Azure/azure-rest-api-specs#18270
[ReCreate this PR](https://github.com/azure-resource-manager-schemas/compare/main...AzureSDKAutomation:sdkAuto/dashboard?expand=1)

Author: msftbot[bot]

schemas/2021-09-01-preview/Microsoft.Dashboard.json

@@ -30,12 +30,12 @@
         },
         "name": {
           "type": "string",
-          "description": "The name of Azure Managed Grafana."
+          "description": "The workspace name of Azure Managed Grafana."
         },
         "properties": {
           "oneOf": [
             {
-              "$ref": "#/definitions/GrafanaResourceProperties"
+              "$ref": "#/definitions/ManagedGrafanaProperties"
             },
             {
               "$ref": "https://schema.management.azure.com/schemas/common/definitions.json#/definitions/expression"
@@ -95,7 +95,7 @@
     }
   },
   "definitions": {
-    "GrafanaResourceProperties": {
+    "ManagedGrafanaProperties": {
       "type": "object",
       "properties": {
         "provisioningState": {