Remove unneeded static casts

[LumioseSil]

We already know that __n, __j, and __m are already integers, so there is no need to use static casts

[StephanTLavavej]

Thanks, good catches. The static_cast removals are definitely great. We often use auto after static_cast to avoid repeating the (sometimes complicated/lengthy) type, but int is the simplest and shortest there is, so I believe that this is reasonable.

[StephanTLavavej]

I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed.

[StephanTLavavej]

Thanks for this code cleanup! 😸 😸 😸 😸 😸