Fix description for ManagedEnvironment.Internal property (Azure#19307)

Author: ruslany

specification/app/resource-manager/Microsoft.App/preview/2022-01-01-preview/ManagedEnvironments.json

@@ -609,7 +609,7 @@
       "properties": {
         "internal": {
           "type": "boolean",
-          "description": "Boolean indicating the environment only has an internal load balancer. These environments do not have a public static IP resource, must provide ControlPlaneSubnetResourceId and AppSubnetResourceId if enabling this property",
+          "description": "Boolean indicating the environment only has an internal load balancer. These environments do not have a public static IP resource. They must provide runtimeSubnetId and infrastructureSubnetId if enabling this property",
           "x-ms-mutability": [
             "create",
             "read"

specification/app/resource-manager/Microsoft.App/stable/2022-03-01/ManagedEnvironments.json

@@ -666,7 +666,7 @@
       "properties": {
         "internal": {
           "type": "boolean",
-          "description": "Boolean indicating the environment only has an internal load balancer. These environments do not have a public static IP resource, must provide ControlPlaneSubnetResourceId and AppSubnetResourceId if enabling this property",
+          "description": "Boolean indicating the environment only has an internal load balancer. These environments do not have a public static IP resource. They must provide runtimeSubnetId and infrastructureSubnetId if enabling this property",
           "x-ms-mutability": [
             "create",
             "read"