Fix "Bad value 1 for attribute autofocus" on special pages

Xml::inputLabel does not work with boolean parameters, therefore change
true to an empty string to avoid the '1' in html.

This is done for Special:BookSources (from the bug),
Special:ExpandTemplates, Special:Undelete and Special:Userrights

Bug: T68134
Change-Id: I53ff5701840750f17a2ea9a1ec56cd88c00f3cf5