Update docstring.
Update docstring.

* subversion/libsvn_ra_svn/client.c
  (open_session): Fix docstring as per current code.


Patch by: Kamesh Jayachandran <kamesh@collab.net>
Tweaked by: me

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion