Fix inconsistent overrides

[aaronmondal]

This caused -Winconsistent-missing-override to complain with Clang 17.

[aaronmondal]

If these are not supposed to be overridden by anything else we could also make them final. This could improve performance. See https://devblogs.microsoft.com/cppblog/the-performance-benefits-of-final-classes/ for an explanation.