Auto merge of #125778 - estebank:issue-67100, r=compiler-errors

Use parenthetical notation for `Fn` traits

Always use the `Fn(T) -> R` format when printing closure traits instead of `Fn<(T,), Output = R>`.

Address #67100:

```
error[E0277]: expected a `Fn()` closure, found `F`
 --> file.rs:6:13
  |
6 |     call_fn(f)
  |     ------- ^ expected an `Fn()` closure, found `F`
  |     |
  |     required by a bound introduced by this call
  |
  = note: wrap the `F` in a closure with no arguments: `|| { /* code */ }`
note: required by a bound in `call_fn`
 --> file.rs:1:15
  |
1 | fn call_fn<F: Fn() -> ()>(f: &F) {
  |               ^^^^^^^^^^ required by this bound in `call_fn`
help: consider further restricting this bound
  |
5 | fn call_any<F: std::any::Any + Fn()>(f: &F) {
  |                              ++++++
```

Author: bors