[clang] [clang][headers][Apple] Don't include_next float.h to avoid an unnecessary module dependency (PR #137432)

[Ian Anderson via cfe-commits]

ian-twilightcoder wrote:

This was originally added in d93779d / d89a1eb (can't find either of these in Phabricator) for `_HAS_SUBNORM`, but that's since been obsoleted by <https://reviews.llvm.org/D37302>. So including this header just causes an unnecessary include and module build of Apple's float.h.

https://github.com/llvm/llvm-project/pull/137432