Remove "Aktionen"-column from list of user stores

What does this MR do?

Removes the "Aktionen"-column from the list of stores that a user is responsible for, on recommendation from @jofranz. The column was apparently broken, and doesn't seem necessary.

Merged manually after a quick rollback

Before:

After:

How confident are you it won't break things if deployed?

Quite.

Checklist

• No test necessary for a small UI change.
• no unrelated changes
• asked someone for a code review
• joined #foodsharing-beta channel at https://slackin.yunity.org
• added an entry to CHANGELOG.md (description, merge request link, username(s))
• Once your MR has been merged, you are responsible to update the #foodsharing-beta Slack channel about what has been changed here. They will test your work in different browsers, roles or other settings