@Override
  protected int submitUnassignProcedure(MasterProcedureEnv env,
    Consumer<TransitRegionStateProcedure> submit) {
    return env.getAssignmentManager()
      .submitUnassignProcedureForClosingExcessRegionReplicas(tableName, newReplicaCount, submit);
  }
Procedure for close excess region replicas.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/procedure/CloseExcessRegionReplicasProcedure.java