debugsetparents: remove redundant invocations of begin/endparentchange

Method localrepo.setparents invokes begin/endparentchange internally,
so there is no need to invoke it explicitly in debugsetparents.

mercurial/commands.py

@@ -3502,9 +3502,7 b' def debugsetparents(ui, repo, rev1, rev2'
     r2 = scmutil.revsingle(repo, rev2, 'null').node()
 
     with repo.wlock():
-        repo.dirstate.beginparentchange()
         repo.setparents(r1, r2)
-        repo.dirstate.endparentchange()
 
 @command('debugdirstate|debugstate',
     [('', 'nodates', None, _('do not display the saved mtime')),