When we spied a fire truck driving down Georgia Avenue on Saturday morning with a banner promoting Muriel Bowser, we were confused. After all, Bowser is a candidate in the coming special election for Ward 4, and last we checked, city vehicles are stricly off-limits for campaign purposes. Well, we weren’t the only ones miffed by the emergency vehicle’s use as a campaign tool. From yesterday’s installment of themail, D.C. Watch’s bi-weekly online newsletter: On…