[Bookmarks Runner] Remove BuildQuery Functor class

Summary:
Instead of constructing the query string on each favicon fetch just use
the (fixed) sql query string.

Test Plan:
make
Switch default "Web browser" in Applications to Chrome/Chromium
Query bookmark with krunner, or e.g.
qdbus-qt5 org.kde.krunner /App org.kde.krunner.App.querySingleRunner bookmarks Phabricator

Reviewers: Frameworks, davidedmundson

Reviewed By: davidedmundson

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D15491