Tweaks space wind probability curve.

Basically, before move_prob would be 50% if the pressure was exactly equal to the atoms resistance value, 100% if it was exactly double, etc.

Now that number is 75% if the difference is exactly pressure_resistance, but we minus 25% from the number, meaning it's still 50% if the difference is exactly pressure_resistance, but it raises and lowers fasters otherwise.

We also don't even attempt to move if the move_prob is lower than 25%, to avoid the issue where even small differences make everything move over time.

code/modules/atmospherics/environmental/LINDA_turf_tile.dm

@@ -250,16 +250,18 @@
 /atom/movable/var/last_high_pressure_movement_air_cycle = 0
 
 /atom/movable/proc/experience_pressure_difference(pressure_difference, direction, pressure_resistance_prob_delta = 0)
+	var/const/PROBABILITY_OFFSET = 25
+	var/const/PROBABILITY_BASE_PRECENT = 75
 	set waitfor = 0
 	. = 0
 	if (!anchored && !pulledby)
 		. = 1
 		if (last_high_pressure_movement_air_cycle < SSair.times_fired)
 			var/move_prob = 100
 			if (pressure_resistance > 0)
-				move_prob = pressure_difference/pressure_resistance*50
+				move_prob = (pressure_difference/pressure_resistance*PROBABILITY_BASE_PRECENT)-PROBABILITY_OFFSET
 			move_prob += pressure_resistance_prob_delta
-			if (prob(move_prob))
+			if (move_prob > PROBABILITY_OFFSET && prob(move_prob))
 				step(src, direction)
 				last_high_pressure_movement_air_cycle = SSair.times_fired