[CosmosDB] Remove ReadOnly tag for PublicNetworkAccess property (#13428)

Author: soeom

specification/cosmos-db/resource-manager/Microsoft.DocumentDB/preview/2021-03-01-preview/cosmos-db.json

@@ -8467,7 +8467,6 @@
     },
     "PublicNetworkAccess": {
       "type": "string",
-      "readOnly": true,
       "description": "Whether requests from Public Network are allowed",
       "enum": [
         "Enabled",

specification/cosmos-db/resource-manager/Microsoft.DocumentDB/preview/2021-03-01-preview/examples/CosmosDBDatabaseAccountCreateMax.json

@@ -31,6 +31,7 @@
             "ignoreMissingVNetServiceEndpoint": false
           }
         ],
+        "publicNetworkAccess": "Enabled",
         "locations": [
           {
             "failoverPriority": 0,
@@ -159,6 +160,7 @@
               "id": "/subscriptions/subId/resourceGroups/rg/providers/Microsoft.Network/virtualNetworks/vnet1/subnets/subnet1"
             }
           ],
+          "publicNetworkAccess": "Enabled",
           "keyVaultKeyUri": "https://myKeyVault.vault.azure.net",
           "enableFreeTier": false,
           "ipRules": [