The wl_pointer.axis_discrete axis (applicable to wl_seat <= v8) is
meant to be sent together with wl_pointer.axis events in the same
frame. And the wl_pointer.axis_value120 event replaces it in
wl_seat >= v9, but has the same relation with the other information
available in a frame.
This emission should not be conditional to anything, so drop the
various checks leading to maybe sending wl_pointer.axis or not.
This fixes emission of wl_pointer.axis in conjunction with discrete
events, for some combinations of versions and (non)value120 mice.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3642>
39d8e44f5e