changed footer of mailanswers

What does this MR do?

changed old foodsharing „Freiwilligenplattform“ mailfooter, which was based on lebensmittelretten

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

sure, just changed a text string, double checked

Links to related issues

Checklist

• added a test, or explain why one is not needed/possible...
• 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))