amend: move obsmarkers creation in the "new changeset" conditional

We already check if we created a new changesets right above this piece of code,
so we can just drop the condition and indent the markers creation.

mercurial/cmdutil.py

@@ -2620,7 +2620,7 b' def amend(ui, repo, commitfunc, old, ext'
                         marks[bm] = newid
                     marks.recordchange(tr)
             #commit the whole amend process
-            if createmarkers and newid != old.node():
+                if createmarkers:
                 # mark the new changeset as successor of the rewritten one
                 new = repo[newid]
                 obs = [(old, (new,))]