remove latest submodule

Author: jo-mueller

.gitmodules

@@ -11,10 +11,6 @@
 	url = https://github.com/jo-mueller/ngff-spec
 	branch = 0.5
 
-[submodule "latest"]
-	path = specifications/latest
-	url = https://github.com/jo-mueller/ngff-spec
-	branch = 0.5
 [submodule "0.4"]
 	path = specifications/0.4
 	url = https://github.com/jo-mueller/ngff-spec