git-gui: Don't delete scrollbars in console windows

git-gui: Don't delete scrollbars in console windows

If we have added a scrollbar to the console window because one
direction has too much text to fit in the available screen space
we should just keep the scrollbars.  Its annoying to watch our
horizontal scrollbar bounce in and out of the window as additional
text is inserted into the widget and the need for the scrollbar
comes and goes.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>