light: don't use rgbw for brightness.

W is basically how washed out it should look. Brightness should only come from
brightness.

custom_components/tuya_local/generic/light.py

@@ -221,10 +221,8 @@ class TuyaLocalLight(TuyaLocalEntity, LightEntity):
                     **settings,
                     **self._color_mode_dps.get_values_to_set(self._device, color_mode),
                 }
-            rgbw = params.get(
-                ATTR_RGBW_COLOR, self.rgbw_color or (0, 0, 0, self.brightness or 255)
-            )
-            brightness = params.get(ATTR_BRIGHTNESS, rgbw[3])
+            rgbw = params.get(ATTR_RGBW_COLOR, self.rgbw_color or (0, 0, 0, 0))
+            brightness = params.get(ATTR_BRIGHTNESS, self.brightness or 255)
             fmt = self._rgbhsv_dps.format
             if rgbw and fmt:
                 rgb = (rgbw[0], rgbw[1], rgbw[2])