Revert "debug onair: add get_duration to nonstop slot"

This reverts commit 4756b493.

panikdb/emissions/models.py

@@ -280,8 +280,5 @@ class Nonstop(models.Model):
     start = models.TimeField()
     end = models.TimeField()
 
-    def get_duration(self):
-            return self.start - self.end
-
     def __unicode__(self):
         return self.title