Update concepts-identity.md

Add a required permission `Microsoft.Network/virtualNetworks/joinLoadBalancer/action`.

Author: nilo19

articles/aks/concepts-identity.md

@@ -182,6 +182,7 @@ The following permissions are needed by the identity creating and operating the
 > | `Microsoft.Network/virtualNetworks/subnets/join/action` | Required to configure the Network Security Group for the subnet when using a custom VNET.|
 > | `Microsoft.Network/publicIPAddresses/join/action` <br/> `Microsoft.Network/publicIPPrefixes/join/action` | Required to configure the outbound public IPs on the Standard Load Balancer. |
 > | `Microsoft.OperationalInsights/workspaces/sharedkeys/read` <br/> `Microsoft.OperationalInsights/workspaces/read` <br/> `Microsoft.OperationsManagement/solutions/write` <br/> `Microsoft.OperationsManagement/solutions/read` <br/> `Microsoft.ManagedIdentity/userAssignedIdentities/assign/action` | Required to create and update Log Analytics workspaces and Azure monitoring for containers. |
+> | `Microsoft.Network/virtualNetworks/joinLoadBalancer/action` | Required to configure the IP-based Load Balancer Backend Pools. |
 
 ### AKS cluster identity permissions