[BUGFIX] Allow removal of RegularExpression validator

Add the missing "delete" button to the RegularExpression
validator for form elements "Telephone" and "Url", allowing
to remove a previously manually added validator again.

Note: The "Email" and "Number" form elements do both also
include validators which are missing the "delete" button. But
since this validators (email validator respectively number
validator) are added automatically on form element creation,
it's considered intended behaviour. Only validators which were
added manually must provide the option to delete them again.

Resolves: #92916
Releases: master, 10.4
Change-Id: I56969395ccb8237af6b48ed1793e1af9afc21423
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/66877


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