webmap is now in maps.txt instead of a config entry (#90821)

## About The Pull Request

Currently the button to open a map in webmap is tied to a config entry,
which would then take the name of the map being played and get the link
to that, however for cases like new/tested/admin uploaded maps where
there is no webmap available, this would still have a link to a url that
doesn't exist.
Instead, we'll make the webmap link be in ``maps.txt``, same as
feedbacklink.

## Why It's Good For The Game

Explained in the about section, this prevents webmaps appearing for maps
that aren't supposed to have a webmap link available.

## Changelog

Nothing player-facing, webmaps aren't currently used (afaik) currently
cause they're broken for tg codebases.

code/modules/client/client_procs.dm

@@ -148,9 +148,9 @@ GLOBAL_LIST_INIT(blacklisted_builds, list(
 			if(!SSmapping.current_map.mapping_url)
 				return
 			if(is_station_level(mob.z))
-				src << link("[SSmapping.current_map.mapping_url][LOWER_TEXT(sanitize_css_class_name(SSmapping.current_map.map_name))]/?x=[mob.x]&y=[mob.y]&zoom=6")
+				src << link("[SSmapping.current_map.mapping_url]/?x=[mob.x]&y=[mob.y]&zoom=6")
 			else
-				src << link("[SSmapping.current_map.mapping_url][LOWER_TEXT(sanitize_css_class_name(SSmapping.current_map.map_name))]")
+				src << link("[SSmapping.current_map.mapping_url]")
 	if (hsrc)
 		var/datum/real_src = hsrc
 		if(QDELETED(real_src))