double title field on product form

2 title fields appears on product creation form. this is a side effect of the recent head backport. head requires node modules to add the field, while this is not necessary with 4.6.

so after the patch for head to add the title field (http://drupal.org/node/32772), here's the patch for 4.6 that removes it :-)

i've also included a fix for bad format_plural usage.

please review and apply if useful.