changes heat exchanger density so they dont just look like you cant w…

…alk over them (#6433)

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:cl:
tweak: tweaked heat exchanger density
/:cl:

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code/modules/atmospherics/machinery/components/unary/heat_exchanger.dm

@@ -4,7 +4,7 @@
 	icon = 'icons/obj/atmospherics/heat_exchanger.dmi'
 	icon_state = "intact"
 	pipe_state = "heunary"
-	density = FALSE
+	density = TRUE
 
 	var/obj/machinery/atmospherics/component/unary/heat_exchanger/partner = null
 	var/update_cycle