refreshLinks.php: Fix fatal when using --category parameter
A title object must be passed to refreshCategory(), which is created in
the above lines, not the string representation received as a parameter.
bug: T172061
Change-Id: Id579a86a26cb438c1866351064c6887dbcea23b0
(cherry picked from commit ec7b5e9262550eb7f3157aa9109abc47b1494f07)