Make it more clear how without_projects works

to avoid ambiguity. See https://gitlab.com/gitlab-org/gitlab/-/issues/217960

doc/api/users.md

@@ -88,7 +88,7 @@ GET /users
 | `order_by`         | string  | no       | Return users ordered by `id`, `name`, `username`, `created_at`, or `updated_at` fields. Default is `id`               |
 | `sort`             | string  | no       | Return users sorted in `asc` or `desc` order. Default is `desc`                                                       |
 | `two_factor`       | string  | no       | Filter users by Two-factor authentication. Filter values are `enabled` or `disabled`. By default it returns all users |
-| `without_projects` | boolean | no       | Filter users without projects. Default is `false`                                                                     |
+| `without_projects` | boolean | no       | Filter users without projects. Default is `false`, which means that all users are returned, with and without projects. |
 | `admins`           | boolean | no       | Return only admin users. Default is `false`                                 |
 
 ```json