[1.6.x] Removed weird unicode char in some de po files

Refs #21601.
[1.6.x] Added 1.6.2 release notes stub.

Backport of ccd80dc3b6 from master
[1.6.x] Fixed #21580 -- Clarified why render() does not return a TemplateResponse object.

Backport of f685f94c98 from master