SystemUI: Use accent color for WiFi progress bar

* Use accent color for WIFi progress bar to avoid violet color when
  animated
* Since we now don't use different colors for night/day, we can also
  remove the file in color-night

Fixes: https://gitlab.com/LineageOS/issues/android/-/issues/3654


Co-authored-by: Michael W. <baddaemon87@gmail.com>
Change-Id: Iaf256c16dc97ba9c5dca6875d5ce847d245b557a