[BUGFIX] Use correct target to trigger file deletion

Use the correct target (clicked button) to be able to access the button name.

Resolves: #90036
Releases: master
Change-Id: I3a2face0c10aa41dea13bc49d3f8f3e9f47b3fcc
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63251


Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Daniel Goerz <daniel.goerz@posteo.de>
Tested-by: TYPO3com <noreply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Daniel Goerz <daniel.goerz@posteo.de>