When an ordinance proposed by initiative petition is passed by the Council in a changed or amended form, and the committee of the petitioners require that such proposed ordinance be submitted to a vote of the electors as provided in Section 16, hereof, the ordinance as passed by the Council shall not take effect until after such vote and, if the proposed ordinance so submitted by approved by a majority of the electors voting thereon, the ordinance as passed by the Council shall be deemed repealed.