chore: premature submodule removed

.gitmodules

@@ -68,12 +68,6 @@
 [submodule "mods/columnia"]
 	path = mods/columnia
 	url = https://git.tchncs.de/Illuna-Minetest/columnia
-[submodule "billboard"]
-	path = billboard
-	url = https://github.com/ClaudiusMinimus/billboard.git
-[submodule "mods/billboard"]
-	path = mods/billboard
-	url = git@github.com:ClaudiusMinimus/billboard.git
 [submodule "mods/hemp"]
 	path = mods/hemp
 	url = https://github.com/pithydon/hemp.git