Dialer: InCallDialpad: Make light numbers visible

* Currently the dialed digits are colored google_grey_300, which is
  not really visible on light background
* Replace with dialer_theme_color_light which is also used on normal
  dialpad and works just fine

Fixes: https://gitlab.com/LineageOS/issues/android/-/issues/6283
Change-Id: I11f7a87b13457a17995b0b46a221f1d3a5009372