[BUGFIX] Fix path to icons in ext:form

One ../ too much, remove it to have the icons working again.

Resolves: #77193
Releases: master
Change-Id: Ifce095548a7eb7af26701a38a301a9a379948aaa
Reviewed-on: https://review.typo3.org/49148


Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Joe Jones <foesse@web.de>
Tested-by: Joe Jones <foesse@web.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>