[evolution] New translatable strings in GSettings scheme

[Milan Crha <mcrha redhat com>]

        Hello,
I just committed a change [1], which adds new translatable strings into
a GSettings scheme file. The strings are:

   Whether unset colors provided in HTML mails.

   If enabled, unset colors in HTML messages, forcing use of desktop
   theme colors instead.

It doesn't change UI at all, neither it shows these texts in the
Evolution UI at all.
        Bye,
        Milan

[1] https://gitlab.gnome.org/GNOME/evolution/commit/4dad3e4c5b7c65a6cf70309ebe818995828abe5d