Disabled new food basket comments while showing pre existing ones for another while

Closes #534 (closed)

What does this MR do?

Disable food basket comments during migration period (max. 3 weeks after release) until there are no pre existing baskets with comments left.

Todo @jofranz after release: remove checks and food basket comment section entirely afterwards

Screenshot (logged in) (updated yellow text - see lang file)

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

Should work.

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))