Previously we allowed users to tweak their font weight to be bold by
setting it manually in their ~/.gitconfig prior to starting git-gui.
This was broken in ae0754ac9a24afa2693246222fc078fe9c133b3a when
Simon set the font weight to normal by default, overridding whatever
we found from the ~/.gitconfig file.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>