Remove extra parameter from `BottomSheet` (#2080)

This PR is to fix the warning which is mentioned in #2079

## Pre-launch Checklist

- [x] I read the [Flutter Style Guide] _recently_, and have followed its
advice.
- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [x] All existing and new tests are passing.

experimental/material_3_demo/lib/component_screen.dart

@@ -1635,7 +1635,7 @@ class BottomSheetSection extends StatefulWidget {
 
 class _BottomSheetSectionState extends State<BottomSheetSection> {
   bool isNonModalBottomSheetOpen = false;
-  PersistentBottomSheetController<void>? _nonModalBottomSheetController;
+  PersistentBottomSheetController? _nonModalBottomSheetController;
 
   @override
   Widget build(BuildContext context) {
@@ -1722,7 +1722,7 @@ class _BottomSheetSectionState extends State<BottomSheetSection> {
                 });
               }
 
-              _nonModalBottomSheetController = showBottomSheet<void>(
+              _nonModalBottomSheetController = showBottomSheet(
                 elevation: 8.0,
                 context: context,
                 // TODO: Remove when this is in the framework https://github.com/flutter/flutter/issues/118619

material_3_demo/lib/component_screen.dart

@@ -1635,7 +1635,7 @@ class BottomSheetSection extends StatefulWidget {
 
 class _BottomSheetSectionState extends State<BottomSheetSection> {
   bool isNonModalBottomSheetOpen = false;
-  PersistentBottomSheetController<void>? _nonModalBottomSheetController;
+  PersistentBottomSheetController? _nonModalBottomSheetController;
 
   @override
   Widget build(BuildContext context) {
@@ -1722,7 +1722,7 @@ class _BottomSheetSectionState extends State<BottomSheetSection> {
                 });
               }
 
-              _nonModalBottomSheetController = showBottomSheet<void>(
+              _nonModalBottomSheetController = showBottomSheet(
                 elevation: 8.0,
                 context: context,
                 // TODO: Remove when this is in the framework https://github.com/flutter/flutter/issues/118619