[pango-display-list] Don't premultiply the colour twice

When rendering a glyph run from a texture we were premultiplying the
colour once in display_list_render() and then again in
display_list_render_texture(). This was causing the color to come out
wrong. This fixes bug #1775.

Thanks to Pierre-Luc Beaudoin for reporting.

clutter/pango/cogl-pango-display-list.c

@@ -240,7 +240,6 @@ _cogl_pango_display_list_render_texture (CoglHandle material,
 {
   CoglColor premult_color = *color;
   cogl_material_set_layer (material, 0, node->d.texture.texture);
-  cogl_color_premultiply (&premult_color);
   cogl_material_set_color (material, &premult_color);
   cogl_set_source (material);