Eliminate a deprecation warning from within our test suite.

* subversion/tests/libsvn_wc/utils.c
  (sbox_wc_revert): Switch to svn_wc_revert5().


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1618865 13f79535-47bb-0310-9956-ffa450edef68