py3: use '%s' instead of %r in hgext/convert/subversion.py
Using '%r' on bytes in python 3 adds b'' prefixes to output which is bad. I
don't see a reason why we want to repr() the string here, so just switched to
'%s'. This fixes some output failure in one of the subversion test.
Differential Revision: https://phab.mercurial-scm.org/D5026
(binary:application/octet-stream)