applets/colorpicker: always send currentColorChanged

GrabWidget returns early if the currentColor is changed to the same color it already is. While this is usually a good idea, it's not here – the color being set only happens when the user has completed picking a color, and the widget needs to be informed about this. There's some extra deduplicating logic there anyway, and re-picking the same color is legitimate - the user may do this to copy it to the clipboard again, or may have deleted it from the history, then reconsidered and now try to re-add it by picking the same color again.

Instead, don't return early if unchanged, and always send the Changed signal.

BUG: 514983 FIXED-IN: 6.6.0