fixes a bug "No expression before quantifier" with Saxon-PE 9.5.1.3

Admittedly, I have no idea what these characters are meant to match (looks somewhat like a uncompleted look behind?! )
Funnily, the error doesn’t arise with current eXist -- but eXist’s dashboard/plugins/userManager/jsjson.xqm (which looks like a direct clone of this file) removes these characters as well.