git-gui: Get rid of the last remnants of GIT_CONFIG_LOCAL

In dc871831(Only use GIT_CONFIG in "git config", not other programs),
GIT_CONFIG_LOCAL was rested in peace, in favor of not reading
/etc/gitconfig and $HOME/.gitconfig at all when GIT_CONFIG is set.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

git-gui.sh

@@ -3329,7 +3329,6 @@ by %s:
 		{^GIT_PAGER$} -
 		{^GIT_TRACE$} -
 		{^GIT_CONFIG$} -
-		{^GIT_CONFIG_LOCAL$} -
 		{^GIT_(AUTHOR|COMMITTER)_DATE$} {
 			append msg " - $name\n"
 			incr ignored_env