video-sink: Remove usage of GL_TEXTURE_2D
video-sink: Remove usage of GL_TEXTURE_2D

GL header files are no longer exposed, and the Clutter Texture we use
are always 2D textures.

ystreet/clutter-gst,lubosz/clutter-gst,GNOME/clutter-gst,GNOME/clutter-gst,ystreet/clutter-gst,lubosz/clutter-gst,ystreet/clutter-gst,GNOME/clutter-gst,ystreet/clutter-gst,GNOME/clutter-gst,lubosz/clutter-gst