Don't show 'Open Graphic Library' to users

This is shown in the list of selected modules in Simple preferences.

modules/video_output/gl.c

@@ -70,7 +70,7 @@ vlc_module_begin ()
 # define API VLC_OPENGL
 # define MODULE_VARNAME "gl"
     set_shortname (N_("OpenGL"))
-    set_description (N_("Open Graphics Library video output"))
+    set_description (N_("OpenGL video output"))
     set_category (CAT_VIDEO)
     set_subcategory (SUBCAT_VIDEO_VOUT)
     set_capability ("vout display", /*170*/0)