Takes the Tram off of the game plane, to make everything on it look a lot less flat (#71858)

## About The Pull Request
That's about it. It being on the game plane sadly had the inherent issue
of "no more ambient occlusion for anything that goes in it", which made
it look jarring.

Sadly, because of this, I had to put regular iron floor tiles over the
pipes/wires/disposals pipes on those crossings, but that's just further
motivation for LT3 and I to work on some new glass plating and actual
glass tiles so we can make this work properly again.

## Why It's Good For The Game
Muh ambient occlusion.

Seriously, it just looks *SO* much better.


## Changelog

🆑 GoldenAlpharex
fix: Everything that goes on the tram should look a lot less flat now!
/🆑

code/game/objects/structures/fluff.dm

@@ -274,7 +274,7 @@
 	icon = 'icons/obj/tram_rails.dmi'
 	icon_state = "rail"
 	layer = TRAM_RAIL_LAYER
-	plane = GAME_PLANE
+	plane = FLOOR_PLANE
 	deconstructible = TRUE
 
 /obj/structure/fluff/tram_rail/floor