Remove unused uc_product_title_sku autocomplete

uc_product_menu() defines an autocomplete callback which is never used:

$ git grep uc_product_title_sku
uc_product/uc_product.module:  $items['autocomplete/uc_product_title_sku'] = array(
uc_product/uc_product.module:    'page callback' => 'uc_product_title_sku_autocomplete',
uc_product/uc_product.pages.inc:function uc_product_title_sku_autocomplete($string = '') {

It looks like this definition, and the entire of uc_product.pages.inc, can be safely removed.