[scrollable_positioned_list] Update for push (#466)

* Update dart SDK to < 4.0.0

* Update changelog and pubspec for version 0.3.6

Author: tarobins

packages/scrollable_positioned_list/pubspec.yaml

@@ -1,11 +1,11 @@
 name: scrollable_positioned_list
-version: 0.3.5
+version: 0.3.6
 description: >
   A list with helper methods to programmatically scroll to an item.
 homepage: https://github.com/google/flutter.widgets/tree/master/packages/scrollable_positioned_list
 
 environment:
-  sdk: '>=2.12.0 <3.0.0'
+  sdk: '>=2.12.0 <4.0.0'
   flutter: '>=2.12.0'
 
 dependencies: