Removed glslang

Maybe it will be returned back in future

Author: Xottab-DUTY

.gitmodules

@@ -61,6 +61,3 @@
 [submodule "Externals/gli"]
 	path = Externals/gli
 	url = https://github.com/g-truc/gli.git
-[submodule "Externals/glslang"]
-	path = Externals/glslang
-	url = https://github.com/KhronosGroup/glslang.git