Update add to app code to run on modern versions of agp and gradle. (#2330)

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

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add_to_app/plugin/flutter_module_using_plugin/lib/cell.dart

@@ -6,7 +6,7 @@ import 'dart:math';
 
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
-import 'package:sensors/sensors.dart';
+import 'package:sensors_plus/sensors_plus.dart';
 
 // This is on alternate entrypoint for this module to display Flutter UI in
 // a (multi-)view integration scenario.
@@ -109,7 +109,7 @@ class _CellState extends State<Cell> with WidgetsBindingObserver {
                         // Don't continuously rebuild for nothing when the
                         // cell isn't visible.
                         stream: appLifecycleState == AppLifecycleState.resumed
-                            ? accelerometerEvents
+                            ? accelerometerEventStream()
                             : Stream.value(defaultPosition),
                         initialData: defaultPosition,
                         builder: (context, snapshot) {

add_to_app/plugin/flutter_module_using_plugin/pubspec.yaml

@@ -11,7 +11,7 @@ dependencies:
     sdk: flutter
   provider: ^6.0.2
   url_launcher: ^6.0.20
-  sensors: ^2.0.3
+  sensors_plus: ^5.0.1
 
 dev_dependencies:
   analysis_defaults: