Mark rsqrt function as noexcept

[AMS21]

Apparently clang-21 will not compile unless we mark rsqrt as noexcept.

Since it just calls _sqrt which is already marked noexcept this should be fine.

[Xottab-DUTY]

Is it ever used? I see that it returns double, which aren't used almost always.

[AMS21]

Is it ever used? I see that it returns double, which aren't used almost always.

You're right it's actually unused. I've updated the PR to instead simply remove the rsqrt function.

[AMS21]

Wait it's not unused. It used right here. No idea how I was able to compile with the rsqrt removed :/

[Xottab-DUTY]

Wait it's not unused. It used right here. No idea how I was able to compile with the rsqrt removed :/

Successfully compiled on Fedora somehow: https://github.com/OpenXRay/xray-16/actions/runs/21565121323/job/62135268722

[Xottab-DUTY]

Thanks!