Remove incorrect system_fbo overwrite

(cherry picked from commit 0198eedb0683682573f19e52d9eef1f18ebca895)

drivers/gles3/storage/texture_storage.cpp

@@ -59,8 +59,6 @@ static const GLenum _cube_side_enum[6] = {
 TextureStorage::TextureStorage() {
 	singleton = this;
 
-	system_fbo = 0;
-
 	{ //create default textures
 		{ // White Textures