ices/75707.rs: fixed with errors

=== stdout ===
=== stderr ===
error[E0277]: the trait bound `MyCall: Callback` is not satisfied
  --> /home/runner/work/glacier/glacier/ices/75707.rs:13:5
   |
7  | fn f<P:Processing+?Sized>() {
   |        ---------- required by this bound in `f`
...
13 |     f::<dyn Processing<Call=MyCall>>();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Callback` is not implemented for `MyCall`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.
==============