Fix issue in NoValueInOnUnimplemented diag

Author: gabrielbusta

compiler/rustc_error_messages/locales/en-US/trait_selection.ftl

@@ -14,4 +14,4 @@ invalid_on_clause_in_rustc_on_unimplemented = invalid `on`-clause in `#[rustc_on
 
 no_value_in_rustc_on_unimplemented = this attribute must have a valid value
     .label = expected value here
-    .note = "eg `#[rustc_on_unimplemented(message="foo")]`"
+    .note = eg `#[rustc_on_unimplemented(message="foo")]`

compiler/rustc_trait_selection/src/errors.rs

@@ -48,9 +48,9 @@ pub struct InvalidOnClauseInOnUnimplemented {
 
 #[derive(SessionDiagnostic)]
 #[diag(trait_selection::no_value_in_rustc_on_unimplemented, code = "E0232")]
+#[note]
 pub struct NoValueInOnUnimplemented {
     #[primary_span]
     #[label]
-    #[note]
     pub span: Span,
 }