[BUGFIX] Prevent XSS in PageLayoutController

Correctly use htmlspecialchars for the link.

Resolves: #82077
Releases: master,8.7,7.6
Change-Id: I87ea4010aa187f5f601c31423fb1a0fc05a23107
Reviewed-on: https://review.typo3.org/53719


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wolfgang Klinger <wolfgang@wazum.com>
Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>