San Diego might cancel its beloved Christmas festival, December Nights , under a cost-cutting proposal by Mayor Todd Gloria. The city is facing a $146 million deficit. So Gloria says no “In Excelsis Deo” on Noël. Residents are furious. Hundreds of thousands of people flock to Balboa Park for the event every year. It’s part of the holiday season in Southern California, just like chilly beach sunsets. Now, the good people of “ America’s Finest City ” might have to do without their Christmas