styles: fix call checkbox color

remove unneeded colorOnPrimary definition from AppThemeBase.Dark

this theme is used in three contexts:
* AppTheme.Call.Base, where colorOnPrimary was causing the checkbox to
  render as a white block. It has no other effect.
* AppTheme.MediaViewer, where the change influences nothing.
* MenuHeader, which appears to be completely unused.

I would have preferred to specify the color in the AppTheme.Call.Base,
but overwriting the value with transparency doesn't appear to work.

GitLab: #1493
Change-Id: Ib3e6ee1b38d08c70210222ce24f6e4b46972719d

jami-android/app/src/main/res/values/styles.xml

@@ -80,7 +80,6 @@
         <item name="colorPrimary">@color/white</item>
         <item name="colorSecondary">@color/color_primary_light</item>
         <item name="colorError">@color/colorError</item>
-        <item name="colorOnPrimary">@color/white</item>
         <item name="colorOnSecondary">@color/white</item>
         <item name="colorPrimaryContainer">@color/colorPrimary</item>
         <item name="colorOnPrimaryContainer">@color/background</item>