set disableLocalAuth to be read-only in swagger (#20358)

Co-authored-by: Bingchen Li <[email protected]>

Author: libc16

specification/machinelearningservices/resource-manager/Microsoft.MachineLearningServices/stable/2022-05-01/machineLearningServices.json

@@ -3218,7 +3218,8 @@
         },
         "disableLocalAuth": {
           "type": "boolean",
-          "description": "Opt-out of local authentication and ensure customers can use only MSI and AAD exclusively for authentication."
+          "description": "Opt-out of local authentication and ensure customers can use only MSI and AAD exclusively for authentication.",
+          "readOnly": true
         }
       },
       "required": [