INTMDB-174: updated an example for cluster (#400)

* docs: updated example for return a connection string in cluster

* docs: added example for azure connection strings

Co-authored-by: Edgar López <[email protected]>

Author: coderGo93

website/docs/r/cluster.html.markdown

@@ -207,9 +207,17 @@ resource "mongodbatlas_cluster" "cluster-test" {
 }
 ```
 ### Example - Return a Connection String
+AWS 
 ```hcl
 output "plstring" {
-    value = lookup(mongodbatlas_cluster.cluster-test.connection_strings[0].aws_private_link_srv, aws_vpc_endpoint.ptfe_service.id)
+    value = lookup(mongodbatlas_cluster.cluster-test.connection_strings[0].private_endpoint[0].srv_connection_string, aws_vpc_endpoint.ptfe_service.id)
+}
+//Example return string: plstring = mongodb+srv://cluster-atlas-pl-0.za3fb.mongodb.net
+```
+Azure
+```hcl
+output "plstring" {
+    value = lookup(mongodbatlas_cluster.cluster-test.connection_strings[0].private_endpoint[0].srv_connection_string, azurerm_private_endpoint.test.id)
 }
 //Example return string: plstring = mongodb+srv://cluster-atlas-pl-0.za3fb.mongodb.net
 ```