stylesets/nord: make unread selected mails readable

Remove the dedicated background color for unread selected
e-mails because it's too close to the foreground color.

Signed-off-by: Max Schillinger <max@mxsr.de>
Acked-by: Robin Jarry <robin@jarry.cc>

stylesets/nord

@@ -33,7 +33,6 @@ msglist_flagged.fg=#a3be8c
 msglist_flagged.bold=true
 
 msglist_unread.fg=#8fbcbb
-msglist_unread.selected.bg=#88C0D0
 
 msglist_pill.reverse=true