Fixes custom vendors not displaying custom item names (#88985)

## About The Pull Request

Something that's really bugged me for a while, custom vendors don't
display custom names on items. Nobody cared enough to fix this but me.
Guess you can count on me, eh?

Tested this on my own private server, worked fine. The items still
technically merge by type, so if you place one item with a custom name
first, then another of the same type with no custom name OR with a
different custom name, the newly inserted item's listed name will
override the other until it's bought.

## Why It's Good For The Game

Fixes https://github.com/tgstation/tgstation/issues/84937 /
https://github.com/tgstation/tgstation/issues/83151 (technically)

## Changelog

🆑
fix: A single enthusiastic chemist hell-bent on selling chemicals to his
co-workers single-handedly solved a programming issue with our custom
vendors. They'll begin displaying custom names (such as those provided
by labels) once more.
/🆑

code/modules/vending/_vending.dm

@@ -1760,9 +1760,11 @@ GLOBAL_LIST_EMPTY(vending_machines_to_restock)
 		if(vending_machine_input[stocked_item] > 0)
 			var/base64
 			var/price = 0
+			var/itemname = initial(stocked_item.name)
 			for(var/obj/item/stored_item in contents)
 				if(stored_item.type == stocked_item)
 					price = stored_item.custom_price
+					itemname = stored_item.name
 					if(!base64) //generate an icon of the item to use in UI
 						if(base64_cache[stored_item.type])
 							base64 = base64_cache[stored_item.type]
@@ -1772,7 +1774,7 @@ GLOBAL_LIST_EMPTY(vending_machines_to_restock)
 					break
 			var/list/data = list(
 				path = stocked_item,
-				name = initial(stocked_item.name),
+				name = itemname,
 				price = price,
 				img = base64,
 				amount = vending_machine_input[stocked_item],