Remove misleading always-true if cfg!(unix)

Author: nabijaczleweli

library/std/src/os/unix/fs.rs

@@ -423,9 +423,7 @@ pub trait OpenOptionsExt {
     /// # fn main() {
     /// let mut options = OpenOptions::new();
     /// options.write(true);
-    /// if cfg!(unix) {
-    ///     options.custom_flags(libc::O_NOFOLLOW);
-    /// }
+    /// options.custom_flags(libc::O_NOFOLLOW);
     /// let file = options.open("foo.txt");
     /// # }
     /// ```