Update samples for Dart 3.0.0 (#1803)

experimental/varfont_shader_puzzle/android/app/build.gradle

@@ -26,6 +26,7 @@ apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
+    namespace "com.example.varfont_shader_puzzle"
     compileSdkVersion flutter.compileSdkVersion
     ndkVersion flutter.ndkVersion
 

experimental/varfont_shader_puzzle/android/app/src/debug/AndroidManifest.xml

@@ -1,5 +1,4 @@
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.example.varfont_shader_puzzle">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <!-- The INTERNET permission is required for development. Specifically,
          the Flutter tool needs it to communicate with the running application
          to allow setting breakpoints, to provide hot reload, etc.

experimental/varfont_shader_puzzle/android/app/src/main/AndroidManifest.xml

@@ -1,5 +1,4 @@
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.example.varfont_shader_puzzle">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <application
         android:label="varfont_shader_puzzle"
         android:name="${applicationName}"

experimental/varfont_shader_puzzle/android/app/src/profile/AndroidManifest.xml

@@ -1,5 +1,4 @@
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.example.varfont_shader_puzzle">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <!-- The INTERNET permission is required for development. Specifically,
          the Flutter tool needs it to communicate with the running application
          to allow setting breakpoints, to provide hot reload, etc.

experimental/varfont_shader_puzzle/android/build.gradle

@@ -26,6 +26,6 @@ subprojects {
     project.evaluationDependsOn(':app')
 }
 
-task clean(type: Delete) {
+tasks.register("clean", Delete) {
     delete rootProject.buildDir
 }