player: remove glClearColor() call at each redraw
player: remove glClearColor() call at each redraw

The clear color is set to black at initialization time. There is no need
to set it again at each frame redraw. So, this call is removed.

Signed-off-by: Julien Olivain <7fdfe229fce69a4d7f38653f3755ccbae5703f88@cotds.org>

jolivain/glslsandbox-player,jolivain/glslsandbox-player,jolivain/glslsandbox-player,jolivain/glslsandbox-player