Any city operating under the council-manager form of government may by ordinance adopted by the council and approved by a two-thirds majority of the qualified electors, voting thereon, at a special or general election in such city, fix the maximum rate of general taxation to be thereafter levied by the council, and also fix the maximum amount of the bonds or other obligations of such city that may be issued, any general or special law applicable to such city to the contrary notwithstanding. However, in the absence of such ordinance or ordinances, so adopted and approved, the maximum rate of general taxation in such city and the maximum amount of the bonds or obligations of such city that may be issued, shall be the same as is provided elsewhere by law or the charter of such city.