irc-network-dialog: Make sure the port GtkSpinButton gets enough space
irc-network-dialog: Make sure the port GtkSpinButton gets enough space

Column expanding was causing the port cell to be eclipsed by the port
spin +/- buttons.

https://bugzilla.gnome.org/show_bug.cgi?id=687361

GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets,Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,GNOME/telepathy-account-widgets