[clang] [clang] Remove FEM_Indeterminable (PR #137661)

[Marius Cornea via cfe-commits]

marius-cornea wrote:

An after-the-fact note: for Intel math libraries, this does not matter at all, as we never use FLT_EVAL_METHOD in our code. We use however other methods to achieve the effect we want, i.e., the equivalent of FLT_EVAL_METHOD = 0 (source). We use fp-model precise, or sometimes strict for that.

https://github.com/llvm/llvm-project/pull/137661