Use parenthetical notation for Fn traits

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

Fix #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: estebank

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -1362,7 +1362,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     match *predicate.self_ty().kind() {
                         ty::Param(param_ty) => Ok((
                             generics.type_param(param_ty, tcx),
-                            predicate.trait_ref.print_only_trait_path().to_string(),
+                            predicate.trait_ref.print_trait_sugared().to_string(),
                         )),
                         _ => Err(()),
                     }

compiler/rustc_const_eval/src/check_consts/ops.rs

@@ -113,7 +113,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
                     if let Some(generics) = tcx.hir_node_by_def_id(caller).generics() {
                         let constraint = with_no_trimmed_paths!(format!(
                             "~const {}",
-                            trait_ref.print_only_trait_path()
+                            trait_ref.print_trait_sugared(),
                         ));
                         suggest_constraining_type_param(
                             tcx,