Remove another redundant function definition in libsvn_repos.

* subversion/libsvn_repos/commit.c
  (check_valid_path): Remove. Was identical to svn_path_check_valid().
  (add_file_or_directory): Update caller, use svn_path_check_valid().


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1481632 13f79535-47bb-0310-9956-ffa450edef68