Update to educe 0.5

I tried doing educe = ">=0.4.6, <0.6", but this happened:

error[E0599]: no method named `debug_struct` found for reference `&String` in the current scope
  --> tests/directly/check_examples/contexts.rs:33:10
   |
33 | #[derive(Educe, Clone)]
   |          ^^^^^ method not found in `&String`
   |
   = note: this error originates in the derive macro `Educe` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0599`.

I suspect this is a bug with educe and older editions.