[DOCS] Fix typo in form documentation

a small typo in the "number range validator" section has been fixed.

Releases: main, 11.5
Resolves: #96312
Change-Id: I3539129f2534bfb87bae55ee37b37e0543b13faa
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/72604


Tested-by: Björn Jacob <bjoern.jacob@tritum.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Björn Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>