[TASK] Release version 1.6.0

Resolves: #59320
Releases: 1.6
Change-Id: I8e336cce4b3b62ae27966b067c4e4686f0b38fed
Reviewed-on: https://review.typo3.org/30575
Reviewed-by: Francois Suter
Tested-by: Francois Suter