[TASK] PHP7 is_numeric change

With PHP 7 the string 0x0 isn't any longer a numeric, so the test
fails. But the test itself makes no sense and is removed.

Resolves: #65320
Releases: master, 6.2
Change-Id: Id7569dfb859ecee7c85c595640515781b1423614
Reviewed-on: http://review.typo3.org/39745


Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>