Makes phoronlocks go to 20C instead of 22 (#6256)

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## About The Pull Request

Title.

## Why It's Good For The Game

22C is too hot for comfort for some species and the phoronlock heaters
are so incredibly powerful that they inevitably heat the entire station
to their temperature, and it really doesn't take long to do so. This is
above the comfort point for some species, so this is an annoyance.

Plus, it being 22C doesn't make it work faster or better or anything.
It's pointless. It runs at max power until it reaches the target
temperature anyway. Turning up the thermostat to make it heat faster
doesn't work in real life or in-game, sorry.

## Changelog

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:cl:
tweak: Phoronlock heaters go to 20 instead of 22
/:cl:

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code/game/machinery/doors/airlock/phoronlocks.dm

@@ -75,7 +75,7 @@
 /obj/machinery/portable_atmospherics/powered/scrubber/huge/stationary/phoronlock		//Special scrubber with bonus inbuilt heater
 	active_power_usage = 2000
 	efficiency_multiplier = 4
-	var/target_temp = T20C + 2
+	var/target_temp = T20C
 	var/heating_power = 150000
 
 /obj/machinery/portable_atmospherics/powered/scrubber/huge/stationary/phoronlock/heater //Variant for use on rift