Revert "UI: Use theme colors setting for Projectors too"

This reverts commit 8a22889e.

After further usage, result is undesirable.  We don't need the theme
applied to projectors.

UI/window-projector.cpp

@@ -67,6 +67,7 @@ OBSProjector::OBSProjector(QWidget *widget, obs_source_t *source_, int monitor,
 		obs_display_add_draw_callback(GetDisplay(),
 				isMultiview ? OBSRenderMultiview : OBSRender,
 				this);
+		obs_display_set_background_color(GetDisplay(), 0x000000);
 	};
 
 	connect(this, &OBSQTDisplay::DisplayCreated, addDrawCallback);