Change default mission duration to 60 minutes.

This seems like it works better for the number of missions we usually
frag, plus the fact that players will almost always choose an ASAP
package.

game/settings.py

@@ -27,7 +27,7 @@ class Settings:
     default_start_type: str = "Cold"
 
     # Mission specific
-    desired_player_mission_duration: timedelta = timedelta(minutes=90)
+    desired_player_mission_duration: timedelta = timedelta(minutes=60)
 
     # Campaign management
     automate_runway_repair: bool = False