§ 115. Limitation on changes. It shall be unlawful during the period of tax exemption, granted pursuant to section one hundred twenty-five of this article, for any redevelopment company or any successor in interest to its title to a project or any part thereof to change or modify any feature of a project for which approval of the planning commission is required by this article, without the approval of such commission, except by a three-quarters vote of the local legislative body.