wireproto: only expose "between" to version 1 of wire protocols
We recently marked other legacy commands as only available to version 1
of the wire protocols. We held off marking "between" because it is
used as part of the SSH handshake.
Since SSH servers assume they are version 1 by default and the
"between" request that is issued as part of the version 2 handshake
is swallowed and not operated on, everything should "just work" if
"between" is not available to version 2.
Differential Revision: https://phab.mercurial-scm.org/D2513