git-gui: Use 'after 1' to post UI rather than tkwait.

The tkwait visibility command and Windows doesn't seem to realize
the window is visible, consequently we are never finishing our
initialization by calling update_status.

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

git-gui

@@ -2337,5 +2337,4 @@ load_all_remotes
 populate_remote_menu .mbar.fetch From fetch_from
 populate_remote_menu .mbar.push To push_to
 populate_pull_menu .mbar.pull
-tkwait visibility .
+after 1 update_status
-update_status