New deprecated_suggestion feature, use in tests

compiler/rustc_feature/src/active.rs

@@ -368,6 +368,8 @@ declare_features! (
     (active, default_alloc_error_handler, "1.48.0", Some(66741), None),
     /// Allows default type parameters to influence type inference.
     (active, default_type_parameter_fallback, "1.3.0", Some(27336), None),
+    /// Allows having using `suggestion` in the `#[deprecated]` attribute.
+    (active, deprecated_suggestion, "1.61.0", Some(94785), None),
     /// Allows `#[derive(Default)]` and `#[default]` on enums.
     (active, derive_default_enum, "1.56.0", Some(86985), None),
     /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`.