Work around a regression in MSVC

Evil Eyerequested to merge
Assumeru/openmw:tieped into master

Remember to vote for https://developercommunity.visualstudio.com/t/Unable-to-compile-this-piece-of-code-wit/10795218

GitHub action: https://github.com/Assumeru/openmw/actions/runs/12239854525

As of 17.12, MSVC complains about these constexpr auto methods. It doesn't care about the non-constexpr ones we've got, and it doesn't care if I replace auto with the actual type.

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