Updating Participant data via csv import won't work

[MSoeb]

Description: The meeting user import has a bug when updating meeting specific data. The data won't be updated. The existing participant is recognized correctly but it will not be updated.

Reproduction:
Precondition: At least one existing participant in a meeting is needed.

1. open a meeting
2. open participants > open three-dot-menu > export current user list as csv
3. open the csv file an > edit some meeting specific data
4. head back to OpenSlides and open participants > open three-dot-menu > choose import
5. import the selected edited file

What should happen:
Updating meeting specific user data should be possible csv reimport of the current participant list.

[rrenkert]

Should be solved by OpenSlides/openslides-backend#1714

[reiterl]

I tested this issue using the instructions, I changed last name and groups, and it worked, so far.
There have been some changes to this import. So I assume, that this issue is already fixed and I close this issue.