elb_target_group: use port parameter as default for target port (#38578)

The docs suggest that `port` parameter is the default port upon
which targets listen. As such, a target need only provide a `Port`
key to override the default.

lib/ansible/modules/cloud/amazon/elb_target_group.py

@@ -502,7 +502,7 @@ def create_or_update_target_group(connection, module):
                     instances_to_add = []
                     for target in params['Targets']:
                         if target['Id'] in add_instances:
-                            instances_to_add.append({'Id': target['Id'], 'Port': int(target['Port'])})
+                            instances_to_add.append({'Id': target['Id'], 'Port': int(target.get('Port', module.params.get('port')))})
 
                     changed = True
                     try: