narrow: remove unrequired compat code for old versions of hg

As the comment says, that if is only required for servers having hg version 3.1
and 3.2. Any client connecting having hg 3.1 or 3.2 locally and trying to use
narrow should already be broken taking in account the changes which have been
done since narrow moved to core.

Differential Revision: https://phab.mercurial-scm.org/D6434

hgext/narrow/narrowbundle2.py

@@ -51,15 +51,11 b' def getbundlechangegrouppart_narrow(bund'
     assert repo.ui.configbool('experimental', 'narrowservebrokenellipses')
 
     cgversions = b2caps.get('changegroup')
-    if cgversions:  # 3.1 and 3.2 ship with an empty value
-        cgversions = [v for v in cgversions
-                      if v in changegroup.supportedoutgoingversions(repo)]
-        if not cgversions:
-            raise ValueError(_('no common changegroup version'))
-        version = max(cgversions)
-    else:
-        raise ValueError(_("server does not advertise changegroup version,"
-                           " can't negotiate support for ellipsis nodes"))
+    cgversions = [v for v in cgversions
+                  if v in changegroup.supportedoutgoingversions(repo)]
+    if not cgversions:
+        raise ValueError(_('no common changegroup version'))
+    version = max(cgversions)
 
     include = sorted(filter(bool, kwargs.get(r'includepats', [])))
     exclude = sorted(filter(bool, kwargs.get(r'excludepats', [])))