wireproto: only expose "debugwireargs" to version 1 transports

I'm not even sure this command should be enabled for version 1
transports. It is just a reflection endpoint for argument data.
We definitely don't need to support it in version 2.

Differential Revision: https://phab.mercurial-scm.org/D3184

mercurial/wireproto.py

@@ -931,7 +931,7 b' def changegroupsubset(repo, proto, bases'
     return wireprototypes.streamres(gen=gen)
 
 @wireprotocommand('debugwireargs', 'one two *',
-                  permission='pull')
+                  permission='pull', transportpolicy=POLICY_V1_ONLY)
 def debugwireargs(repo, proto, one, two, others):
     # only accept optional args from the known set
     opts = options('debugwireargs', ['three', 'four'], others)