Update README.md (#1024)

The field `user` in the `gateway_role_user_assignements` role is not handling well the `id` of the user, so, only the user's `username` is working correctly

Co-authored-by: David Danielsson <[email protected]>

Author: ivarmu

roles/gateway_role_user_assignments/README.md

@@ -55,7 +55,7 @@ Options for the `role_user_assignments` variable:
 | Variable Name       | Default Value | Required | Type | Description                                                                                           |
 |:--------------------|:-------------:|:--------:|:----:|:------------------------------------------------------------------------------------------------------|
 | `role_definition`   |      N/A      |   yes    | str  | The name or id of the role definition to assign to the user.                                          |
-| `user`              |      N/A      |    no    | str  | The username or id of the user to assign to the object.                                               |
+| `user`              |      N/A      |    no    | str  | The username of the user to assign to the object.                                                     |
 | `user_ansible_id`   |      N/A      |    no    | str  | Resource id of the user who will receive permissions from this assignment. Alternative to user field. |
 | `object_id`         |      N/A      |    no    | int  | Primary key of the object this assignment applies to.                                                 |
 | `object_ansible_id` |      N/A      |    no    | str  | Resource id of the object this role applies to. Alternative to the object_id field.                   |