convert: don't pass --no-files to "darcs show repo" command

The test fails with darcs 2.14.0 because --no-files is no longer supported.
It was removed at the patch 97973a52bf496657558412562d6fad2ee651b1e0, which
says "show repo: removed --files option, removed manual flags parsing."

As far as I can tell, --no-files was specified just for optimization, so old
darcs should work without it.

hgext/convert/darcs.py

@@ -126,8 +126,7 b' class darcs_source(common.converter_sour'
         return etree.getroot()
 
     def format(self):
-        output, status = self.run('show', 'repo', no_files=True,
-                                  repodir=self.path)
+        output, status = self.run('show', 'repo', repodir=self.path)
         self.checkexit(status)
         m = re.search(r'^\s*Format:\s*(.*)$', output, re.MULTILINE)
         if not m: