fixes an isssue with a leftover color_coord shader attribute in defaultvertexshader

these were changed to "color,"  which was overlooked in one shader.

Signed-off-by: tgfrerer <tim@poniesandlight.co.uk>
Merge pull request #2262 from tgfrerer/fix-color_coord-leftover

fixes an isssue with a leftover color_coord shader attribute