df/uniq: suppress lint errors

[cakebaker]

This PR is more of a workaround and suppresses a clippy lint error that was introduced with Rust 1.61.

I don't know how to fix this in a clean way because of some magic behavior of writeln! I couldn't figure out (it adds df: to the output when it's called the first time, but not in subsequent calls). This was also the reason I used eprintln!...

[sylvestre]

maybe also

error: unnecessary structure name repetition
  --> src\uu\uniq\src/uniq.rs:37:6
   |
37 | enum Delimiters {
   |      ^^^^^^^^^^ help: use the applicable keyword: `Self`
   |
   = note: `-D clippy::use-self` implied by `-D warnings`
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#use_self

?

[cakebaker]

With uniq it seems to be a false positive bug: rust-lang/rust-clippy#6902

[sylvestre]

thanks