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

Closes llvm#124652.

This header was introduced in
llvm@5367369,
but it appears that including only `fnctl.h` should be enough.
Hopefully, this patch will not cause build issues on other Unix
platforms.

Author: c8ef

llvm/lib/Support/Unix/Path.inc

@@ -29,7 +29,6 @@
 
 #include <dirent.h>
 #include <pwd.h>
-#include <sys/file.h>
 
 #ifdef __APPLE__
 #include <copyfile.h>