PITTSBURGH — Hillary Clinton is so over Donald Trump.Using some of her most dismissive language of the campaign, Clinton said aboard her campaign plane on Saturday that, “I don’t even think about responding to him anymore” after their third and final debate earlier this week.Leading in the polls both nationally and in battleground states, Clinton signaled that she and running mate Tim Kaine instead would be focused on making gains for congressional Democrats in the closing stretch of the campaign.