Rollup merge of #127878 - estebank:assoc-item-removal, r=fmease

Fix associated item removal suggestion

We were previously telling people to write what was already there, instead of removal (treating it as a `help`). We now properly suggest to remove the code that needs to be removed.

```
error[E0229]: associated item constraints are not allowed here
  --> $DIR/E0229.rs:13:25
   |
LL | fn baz<I>(x: &<I as Foo<A = Bar>>::A) {}
   |                         ^^^^^^^ associated item constraint not allowed here
   |
help: consider removing this associated item binding
   |
LL - fn baz<I>(x: &<I as Foo<A = Bar>>::A) {}
LL + fn baz<I>(x: &<I as Foo>::A) {}
   |
```

compiler/rustc_hir_analysis/src/hir_ty_lowering/errors.rs

@@ -1257,14 +1257,12 @@ pub fn prohibit_assoc_item_constraint(
             };
 
             // Now emit the suggestion
-            if let Ok(suggestion) = tcx.sess.source_map().span_to_snippet(removal_span) {
-                e.span_suggestion_verbose(
-                    removal_span,
-                    format!("consider removing this associated item {}", constraint.kind.descr()),
-                    suggestion,
-                    Applicability::MaybeIncorrect,
-                );
-            }
+            e.span_suggestion_verbose(
+                removal_span,
+                format!("consider removing this associated item {}", constraint.kind.descr()),
+                "",
+                Applicability::MaybeIncorrect,
+            );
         };
 
         // Suggest replacing the associated item binding with a generic argument.