tests: directly 'getchangegroup'

It is identical to 'getlocalchangegroup' with a shorter name.

tests/test-bundle2-format.t

@@ -113,7 +113,7 b' Create an extension to test bundle2 API'
   >             headmissing = [c.node() for c in repo.set('heads(%ld)', revs)]
   >             headcommon  = [c.node() for c in repo.set('parents(%ld) - %ld', revs, revs)]
   >             outgoing = discovery.outgoing(repo, headcommon, headmissing)
-  >             cg = changegroup.getlocalchangegroup(repo, 'test:bundle2', outgoing)
+  >             cg = changegroup.getchangegroup(repo, 'test:bundle2', outgoing)
   >             bundler.newpart('changegroup', data=cg.getchunks(),
   >                             mandatory=False)
   >