www/phpvirtualbox{,-legacy}: PHP 8 support (1 more catch) - "preg_replace"

Fixed:
PHP Warning: preg_replace() expects at least 3 parameters, 2 given in endpoints/screen.php on line 91

PR: 261498
Approved by: tcberner (mentor)
MFH: 2023Q3

(cherry picked from commit 3f1b38acfda124fc8f03fe5f4edfef10ef214501)