Remove an unused special case from the ExpectedOutput classes in the test
suite.

* subversion/tests/cmdline/svntest/verify.py
  (ExpectedOutput): Assert that 'expected' is not None, and remove the tiny
    bit of support for that case. Update a comment after r1443242.
  (AnyOutput): Initialize the expected output to [] instead of None.
  (compare_and_display_lines): Assert that 'expected' is not None. Document
    the 'actual' parameter.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1443263 13f79535-47bb-0310-9956-ffa450edef68