use httpAssembleURI not httpAssembleURIf

Summary:
the latter is for when the last argument is a format string. which I
believe is not the case here. or perhaps more importantly if it was a
format string it'd be an invalid call because we pass no values in

Test Plan:
- make two printers
- pause them
- print job to one printer
- open printer queue
- right click job to move to other printer
- job is now on other printer

Reviewers: dantti

Reviewed By: dantti

Subscribers: kde-utils-devel

Differential Revision: https://phabricator.kde.org/D28479