coreutils: remove invalid fallback for symlinks from binary_path

[oech3]

current_exe() (/proc/self/exe) resolves symlink. So args.next.unwrap() is the best effort at here and empty arg does not happen generally.

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/cut/bounded-memory (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/date/date-locale-hour (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/retry (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/symlink (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/misc/tty-eof (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/inotify-dir-recreate (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/basenc/bounded-memory is now passing!
Congrats! The gnu test tests/seq/seq-epipe is now passing!

[sylvestre]

what is the issue you are trying to fix ?

[oech3]

It this is reachable code, it potentially resolves incorrect utility name. I want to avoid it.
If this is unreachable code, it should be removed.