vim: do not autoenable the mouse

The mouse being autoenabled is just annoying in xfce4-terminal (mouse
drag make vim go into visual mode and there is no right click menu),
so remove the setting for xfce.

Signed-off-by: Jackie Huang <jackie.huang@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>