[TASK] Remove PHP bug workaround in GIFBUILDER

TYPO3 has a bound box calculation workaround due to a PHP bug,
which was fixed in PHP 7.0.12 / 7.1, which can now safely be
removed.

Resolves: #85232
Releases: master
Change-Id: I72e9ea925ae7e91eea244b89a20b1bec2408ca78
Reviewed-on: https://review.typo3.org/57196


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>