On the fsx-id branch:  Get rid of an unnecessary intermediary function.

* subversion/libsvn_fs_x/dag.h
  (svn_fs_x__dag_remove_node): Remove declaration.

* subversion/libsvn_fs_x/dag.c
  (svn_fs_x__dag_remove_node): Remove implementation.
  (svn_fs_x__dag_delete_if_mutable): Call svn_fs_x__delete_node_revision
                                     directly as we know the node is mutable.

git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/fsx-id@1647807 13f79535-47bb-0310-9956-ffa450edef68