Follow-up to r1535330: fix a typo that broke the binding tests

* subversion/libsvn_repos/log.c
  (turn_moves_into_copies): 'V' denotes moves, not 'M'

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1535341 13f79535-47bb-0310-9956-ffa450edef68