Rollup merge of #138343 - tgross35:f16-powf, r=joboet

Enable `f16` tests for `powf`

The LLVM issue [1] was fixed with [2], which is included in the LLVM20 upgrade. Tests no longer fail, so enable them here.

[1]: https://github.com/llvm/llvm-project/pull/98681
[2]: https://github.com/llvm/llvm-project/pull/98681

try-job: aarch64-gnu
try-job: x86_64-gnu-aux