Fix doc TODO (#136485)

Underlying bug (https://github.com/dart-lang/dartdoc/issues/2276) has been fixed a while ago.

packages/flutter/lib/src/services/text_formatter.dart

@@ -265,8 +265,7 @@ class FilteringTextInputFormatter extends TextInputFormatter {
   ///
   /// If [allow] is true, then the filter pattern is an allow list,
   /// and characters must match the pattern to be accepted. See also
-  /// the `FilteringTextInputFormatter.allow` constructor.
-  // TODO(goderbauer): Cannot link to the constructor because of https://github.com/dart-lang/dartdoc/issues/2276.
+  /// the [FilteringTextInputFormatter.allow()] constructor.
   ///
   /// If [allow] is false, then the filter pattern is a deny list,
   /// and characters that match the pattern are rejected. See also