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.
#require docutils gettext
$ $TESTDIR/check-gendoc sv
checking for parse errors