Follow-up to r1464407, fix a copy-pasto:

* subversion/include/svn_error_codes.h
  (SVN_ERR_RA_CANNOT_CREATE_TUNNEL): Really use a new error code.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1464409 13f79535-47bb-0310-9956-ffa450edef68