This MR locks the header colours of Breeze Dark and Breeze Light, for
Plasma 5.21/master, to the colours for the titlebars and window colours
that they currently use in 5.20 (from their respective colour schemes),
so that the locked appearance is consistent with how the background of
these Plasma Styles is already locked, as well as fixing an issue with
the header looking wrong on light colour schemes + Breeze Dark and
vice-versa. Breeze itself will still colour just as completely as usual,
though.
BUG: 427864
FIXED-IN: 5.76
79cbd1ba74