fix: copy_file_range fd_in arg on Linux/Android

[SteveLauC]

What does this PR do

Fix the fd_in argument of the copy_file_range(2) syscall on Linux/Andorid

Checklist:

• I have read CONTRIBUTING.md
• I have written necessary tests and rustdoc comments
• A change log has been added if this PR modifies nix's API

Well, I have no idea how the test passed before this...

[SteveLauC]

Oh I get it now, our unit test is using BorrowedFd, which has the same memory representation as RawFd, so it passed without any issue, in my use case, I was using a reference to a File, so I got the EBADF error

[asomers]

Good catch, but why [skip ci]?

[SteveLauC]

but why [skip ci]?

To save our cirrus CI usage, but it should be needless now, let me remove it