flights: contrailChance back to 0.85 (1.00 was a test value)

config.js

@@ -174,7 +174,7 @@ window.CONFIG = {
         wStrip: 1,
         // Contrails: contrailChance of the aircraft leaves a trail once
         // above contrailStartKm, visible for contrailLifeS seconds.
-        contrailChance: 1.00,
+        contrailChance: 0.85,
         contrailStartKm: 6,
         contrailLifeS: 300,
         contrailWidthM: 620,      // full trail width