[TASK] Deprecate the $icon setter/getter in the Extbase Category model

Resolves: #75904
Releases: master
Change-Id: Ifa27348ae8204af7cac777756282016a88b0be6b
Reviewed-on: https://review.typo3.org/48034


Reviewed-by: Nicole Cordes <typo3@cordes.co>
Reviewed-by: Paul Ilea <paul@target-e.com>
Reviewed-by: Marcin Krzyżanowski <m.krzyzanowski@macopedia.pl>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>