copies: delete misplaced comment The comment was added in 78d760aa3607 (duplicatecopies: do not mark items not in the dirstate as copies, 2013-03-28). It became misplaced in 3666331164bb (cmdutil: add copy-filtering support to duplicatecopies, 2014-06-07). Then the relevant code was moved far away in 754b5117622f (context: add workingfilectx.markcopied, 2017-10-15). Differential Revision: https://phab.mercurial-scm.org/D6352