Follow-up to r1442645:

* subversion/tests/cmdline/input_validation_tests.py
  (invalid_diff_targets): This test is expecting 'svn diff' to throw an error
   but the syntax it is using is valid as of r1442645. Add another target to
   the 'diff' invocation to make this test use invalid syntax again.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1442656 13f79535-47bb-0310-9956-ffa450edef68