§ 5-207 Alteration of rates prohibited. It shall be unlawful for the city to make, or cause to be made, any alteration of rates or charges affecting any item or source of the revenues of the several sinking funds established prior to July first, nineteen hundred eighty-one or of the general fund which may tend to a diminution of the receipts from such sources of revenue, or either of them, except that it shall be lawful for the city to exempt places of public worship from the payment of any fee for the construction of vaults under the sidewalk or in front thereof.