[RTF] Missing supporters in Motion export

[Elblinator]

Description:
If a motion has supporters and is exported. the supporters are never visible in the exported document

Reproduction:

1. in a meeting > settings > motions-settings > set "number of (minimum)required supporters to a motion" to one
2. allow your user to support motions -> participants > (three dots menu) groups > activate "can support motions"
3. allow to support a motion in a specific state -> motions > (three dot menu) workflows > one specific workflow > activate "allow support" (remember the workflow and the state)
4. set yourself to present
5. create a new motion, and make sure that you are not the submitter yourself
6. in the new motion put the state to the state which can be supported
7. support the motion
8. in motion-list > three dot menu > export > pdf and supporter users
9. the supporters in the pdf are missing

Wanted behaviour:
the supporters should be correctly exported and displayed in the pdf