[TASK] Use correct regexp character class

Use [:xdigit:] (a-f0-9/i) instead of [:alnum:] (a-z0-9/i)
for parsing hexadecimal values in sequences.

Resolves: #90263
Releases: master
Change-Id: I26d575c381a17c409abcd5ed04876696587a3886
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/63078


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>