Do not enable Scintilla's Change History by default (#3591)
* It looks either a bit confusing or to have some bugs (without having
investigated deeply, it did things I didn't understand);
* It marks all lines when reloading a file (instead of resetting to a
blank slate);
* If marker margin is not visible, it can render the editor unreadable
with the default settings;
* I don't see any obvious use case given its current behavior that
warrants a so visible feature by default;
* I don't think the feature is obvious at first glance, which could
easily lead users to wonder what that line is about. It also looks
similar to other editor's VCS commit status indicator (including
git-changebar Geany plugin) display, yet behaves very differently,
possibly increasing confusion.
So for now, I think it's better to have it disabled by default.