enable lint prefer_generic_function_type_aliases (#21680)

dev/manual_tests/lib/material_arc.dart

diff --git a/dev/manual_tests/lib/material_arc.dart b/dev/manual_tests/lib/material_arc.dart
index e4afb81..06cdf9f 100644
--- a/dev/manual_tests/lib/material_arc.dart
+++ b/dev/manual_tests/lib/material_arc.dart
@@ -396,7 +396,7 @@
   }
 }
 
-typedef Widget _DemoBuilder(_ArcDemo demo);
+typedef _DemoBuilder = Widget Function(_ArcDemo demo);
 
 class _ArcDemo {
   _ArcDemo(this.title, this.builder, TickerProvider vsync)

dev/manual_tests/lib/overlay_geometry.dart

diff --git a/dev/manual_tests/lib/overlay_geometry.dart b/dev/manual_tests/lib/overlay_geometry.dart
index e73cb75..3f1cb37 100644
--- a/dev/manual_tests/lib/overlay_geometry.dart
+++ b/dev/manual_tests/lib/overlay_geometry.dart
@@ -92,7 +92,7 @@
   OverlayGeometryAppState createState() => OverlayGeometryAppState();
 }
 
-typedef void CardTapCallback(GlobalKey targetKey, Offset globalPosition);
+typedef CardTapCallback = void Function(GlobalKey targetKey, Offset globalPosition);
 
 class CardBuilder extends SliverChildDelegate {
   CardBuilder({ this.cardModels, this.onTapUp });