Github "suggestion" feature has a different markdown format, it uses:

    ```suggestion
    SUGGESTION
    ```

While Gitlab has a _range_ in the suggestion markdown, like:

    ```suggestion-0+0
    SUGGESTION
    ```

To convert the Github format to Gitlab, in the `DiffNote`
_representation_ the range will be added. The range is calculated by the
difference of the `start_line` and `line` when the start_line is
present, which indicates a multi-line suggestion.

Related to: https://gitlab.com/gitlab-org/gitlab/-/issues/340624

Changelog: changed
MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/71411