Any pledge of taxes pursuant to Section 33641 of the Health and Safety Code made with respect to taxes imposed under Section 7202.6 to the payment of principal and interest on bonds of a redevelopment agency shall constitute the obligation of a contract between the redevelopment agency and the holder of the bonds and shall be protected from impairment by the United States and California Constitutions. The provisions of Section 7202.6 which authorize the imposition of the taxes may not be repealed during the time that any of the bonds remain outstanding.