For reasons unclear to me, fish enables bold mode unconditionally if
the background is set.
However, this called a background "set" if it wasn't exactly the
"normal" color, whereas set_color --print-colors would set a color
of *none*.
We have three special non-color colors:
- "normal"
- "reset"
- "none"
All of these specify some form of absence of background color, so all
of them should be checked.
Fixes#7805
4762d52e52