Clean up svn:mergeinfo properties.

During the r32872 catch-up merge, I merged the file "merge_authz_tests.py"
in two steps to work around a problem whereby the automatic merge failed.
This resulted in explicit mergeinfo on the file that was unnecessary (and
perhaps wrong; I'm not sure). Since this "subtree mergeinfo" causes svn
1.5.2's "merge --reintegrate" to fail, I am removing it.

* subversion/tests/cmdline/merge_authz_tests.py
  Remove the "svn:mergeinfo" property.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/double-delete@872969 13f79535-47bb-0310-9956-ffa450edef68