[TASK] Remove unused code in GraphicsFunctions

$this->cmds['jpg'] gets set but is overwritten again a few
lines below.

Resolves: #78815
Releases: master
Change-Id: I9136b055e4eb3927249d8eb97486f36ad3a8976c
Reviewed-on: https://review.typo3.org/50790


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>