Revert "allow disabling of runcommand (#15092)" (#15147)

This reverts commit ec3e241.

Author: haitch

specification/containerservice/resource-manager/Microsoft.ContainerService/stable/2021-07-01/examples/ManagedClustersCreate_DisableRunCommand.json

@@ -541,9 +541,6 @@
           "Create Managed Private Cluster with Public FQDN specified": {
             "$ref": "./examples/ManagedClustersCreate_PrivateClusterPublicFQDN.json"
           },
-          "Create Managed Cluster with RunCommand disabled": {
-            "$ref": "./examples/ManagedClustersCreate_DisableRunCommand.json"
-          },
           "Create Managed Cluster with Node Public IP Prefix": {
             "$ref": "./examples/ManagedClustersCreate_NodePublicIPPrefix.json"
           },
@@ -3533,10 +3530,6 @@
         "enablePrivateClusterPublicFQDN": {
           "type": "boolean",
           "description": "Whether to create additional public FQDN for private cluster or not."
-        },
-        "disableRunCommand": {
-          "type": "boolean",
-          "description": "Whether to disable run command for the cluster or not."
         }
       },
       "description": "Access profile for managed cluster API server."