Fix swagger correctness: secrets were wrongfully marked as write-only (Azure#17228)

* allow accessKeys to be readable

* add x-ms-identifiers

* remove x-ms-identifier

Author: juniwang

specification/signalr/resource-manager/Microsoft.SignalRService/stable/2021-10-01/signalr.json

@@ -1923,38 +1923,22 @@
         "primaryKey": {
           "description": "The primary access key.",
           "type": "string",
-          "x-ms-secret": true,
-          "x-ms-mutability": [
-            "create",
-            "update"
-          ]
+          "x-ms-secret": true
         },
         "secondaryKey": {
           "description": "The secondary access key.",
           "type": "string",
-          "x-ms-secret": true,
-          "x-ms-mutability": [
-            "create",
-            "update"
-          ]
+          "x-ms-secret": true
         },
         "primaryConnectionString": {
           "description": "Connection string constructed via the primaryKey",
           "type": "string",
-          "x-ms-secret": true,
-          "x-ms-mutability": [
-            "create",
-            "update"
-          ]
+          "x-ms-secret": true
         },
         "secondaryConnectionString": {
           "description": "Connection string constructed via the secondaryKey",
           "type": "string",
-          "x-ms-secret": true,
-          "x-ms-mutability": [
-            "create",
-            "update"
-          ]
+          "x-ms-secret": true
         }
       }
     },

specification/webpubsub/resource-manager/Microsoft.SignalRService/stable/2021-10-01/webpubsub.json

@@ -2377,38 +2377,22 @@
         "primaryKey": {
           "description": "The primary access key.",
           "type": "string",
-          "x-ms-secret": true,
-          "x-ms-mutability": [
-            "create",
-            "update"
-          ]
+          "x-ms-secret": true
         },
         "secondaryKey": {
           "description": "The secondary access key.",
           "type": "string",
-          "x-ms-secret": true,
-          "x-ms-mutability": [
-            "create",
-            "update"
-          ]
+          "x-ms-secret": true
         },
         "primaryConnectionString": {
           "description": "Connection string constructed via the primaryKey",
           "type": "string",
-          "x-ms-secret": true,
-          "x-ms-mutability": [
-            "create",
-            "update"
-          ]
+          "x-ms-secret": true
         },
         "secondaryConnectionString": {
           "description": "Connection string constructed via the secondaryKey",
           "type": "string",
-          "x-ms-secret": true,
-          "x-ms-mutability": [
-            "create",
-            "update"
-          ]
+          "x-ms-secret": true
         }
       }
     },