Revert "Command to allow geofence action to be set per-fence (#1482)"

[bkueng]

This reverts commit 6652031.

There's a problem with the C library generator:
The addition of MAV_CMD to development.xml led to the removal
of MAV_CMD in common.h. This breaks build for everyone using that enum
and including 'common.h' or 'standard.h' (and probably others).
See mavlink/c_library_v2@992871b

@hamishwillee agreed to revert this until we have a correct fix.

[olliw42]

@bkueng
just in case it might be helpful
this is ultimately a problem of the generator, you can however often circumvent it by careful arrangement of the order of dialects here https://github.com/mavlink/mavlink/blob/master/scripts/update_c_library.sh#L63-L69
you need to choose the order such that "higher" dialects don't overwrite "lower" dialects
it can be logically understood but it is a bit weird, so a bit testing might be needed
I have not tested, but I guess I would try to swap the calls to standard and development

(few months ago I did a fix in mavgen but threw it away)(this issue was btw one reason I went away from mavgen LOL)