patchbomb: don't close unused progress topic

The "writing" topic has not been used since 1830d0cc4bc1 (patchbomb:
minor refactoring of mbox functionality, preparing for move,
2011-11-23).

Differential Revision: https://phab.mercurial-scm.org/D3803

hgext/patchbomb.py

@@ -801,5 +801,4 b' def email(ui, repo, *revs, **opts):'
             generator.flatten(m, 0)
             sendmail(sender_addr, to + bcc + cc, fp.getvalue())
 
-    ui.progress(_('writing'), None)
     ui.progress(_('sending'), None)