[MIRROR] Use base_icon_state for smart fridge content overlay [MDB IGNORE] (#26063)

* Use `base_icon_state` for smart fridge content overlay (#80825)

## About The Pull Request
No need to create a separate var called `contents_icon_state` when we
already have `base_icon_state`. Save some memory from creating an extra
var

## Changelog
🆑
code: smart fridge content overlay now uses `base_icon_state` instead of
a separate var
/🆑

* Use `base_icon_state` for smart fridge content overlay

* There we go.

---------

Co-authored-by: SyncIt21 <110812394+SyncIt21@users.noreply.github.com>
Co-authored-by: Useroth <37159550+Useroth@users.noreply.github.com>

modular_skyrat/modules/primitive_structures/code/storage_structures.dm

@@ -58,7 +58,7 @@
 	icon = 'modular_skyrat/modules/primitive_structures/icons/storage.dmi'
 	resistance_flags = FLAMMABLE
 	base_build_path = /obj/machinery/smartfridge/producebin
-	contents_icon_state = "produce"
+	base_icon_state = "produce"
 	use_power = NO_POWER_USE
 	light_power = 0
 	idle_power_usage = 0
@@ -89,7 +89,7 @@
 	icon = 'modular_skyrat/modules/primitive_structures/icons/storage.dmi'
 	resistance_flags = FLAMMABLE
 	base_build_path = /obj/machinery/smartfridge/seedshelf
-	contents_icon_state = "seed"
+	base_icon_state = "seed"
 	use_power = NO_POWER_USE
 	light_power = 0
 	idle_power_usage = 0
@@ -119,7 +119,7 @@
 	icon = 'modular_skyrat/modules/primitive_structures/icons/storage.dmi'
 	resistance_flags = FLAMMABLE
 	base_build_path = /obj/machinery/smartfridge/rationshelf
-	contents_icon_state = "ration"
+	base_icon_state = "ration"
 	use_power = NO_POWER_USE
 	light_power = 0
 	idle_power_usage = 0
@@ -149,7 +149,7 @@
 	icon = 'modular_skyrat/modules/primitive_structures/icons/storage.dmi'
 	resistance_flags = FLAMMABLE
 	base_build_path = /obj/machinery/smartfridge/producedisplay
-	contents_icon_state = "nonfood"
+	base_icon_state = "nonfood"
 	use_power = NO_POWER_USE
 	light_power = 0
 	idle_power_usage = 0