context: delete mistaken comment about return value of renamed()
The comment seems to think that the return value of renamed() is a
tuple of source pathsx in the parents, but it's actually a pair of
(rename source path, file nodeid).
Differential Revision: https://phab.mercurial-scm.org/D5639
#require docutils gettext
$ $TESTDIR/check-gendoc ru
checking for parse errors