[llvm] [NFC] Remove redundant `sys/file.h` header. (PR #124684)

[via llvm-commits]

c8ef wrote:

> Consider mentioning [5367369](https://github.com/llvm/llvm-project/commit/536736995bf5d073853c7e884968c9847b4ae64d) in the commit message when you merge this

Done.



https://github.com/llvm/llvm-project/pull/124684