Delete fast start unit test (#67757)

Now that fast-start syncs assets by default, this isn't testing anything. Retire the test

dev/devicelab/bin/tasks/gradle_fast_start_test.dart

-// Copyright 2014 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-import 'package:flutter_devicelab/framework/apk_utils.dart';
-import 'package:flutter_devicelab/framework/framework.dart';
-import 'package:flutter_devicelab/framework/task_result.dart';
-import 'package:flutter_devicelab/framework/utils.dart';
-
-Future<void> main() async {
-  await task(() async {
-    try {
-      await runPluginProjectTest((FlutterPluginProject pluginProject) async {
-        section('APK content for task assembleDebug with --fast-start');
-        await pluginProject.runGradleTask('assembleDebug',
-            options: <String>['-Pfast-start=true']);
-
-        final Iterable<String> apkFiles = await getFilesInApk(pluginProject.debugApkPath);
-
-        checkCollectionContains<String>(<String>[
-          ...debugAssets,
-          ...baseApkFiles,
-          'lib/x86/libflutter.so',
-          'lib/x86_64/libflutter.so',
-          'lib/armeabi-v7a/libflutter.so',
-          'lib/arm64-v8a/libflutter.so',
-        ], apkFiles);
-
-        checkCollectionDoesNotContain<String>(<String>[
-          ...flutterAssets,
-        ], apkFiles);
-      });
-
-      return TaskResult.success(null);
-    } on TaskResult catch (taskResult) {
-      return taskResult;
-    } catch (e) {
-      return TaskResult.failure(e.toString());
-    }
-  });
-}

dev/prod_builders.json

@@ -60,12 +60,6 @@
          "task_name": "linux_fuchsia_precache",
          "flaky": false
       },
-      {
-         "name": "Linux gradle_fast_start_test",
-         "repo": "flutter",
-         "task_name": "linux_gradle_fast_start_test",
-         "flaky": false
-      },
       {
          "name": "Linux gradle_jetifier_test",
          "repo": "flutter",
@@ -186,12 +180,6 @@
          "task_name": "mac_framework_tests",
          "flaky": false
       },
-      {
-         "name": "Mac gradle_fast_start_test",
-         "repo": "flutter",
-         "task_name": "mac_gradle_fast_start_test",
-         "flaky": false
-      },
       {
          "name": "Mac gradle_jetifier_test",
          "repo": "flutter",
@@ -300,12 +288,6 @@
          "task_name": "win_framework_tests",
          "flaky": false
       },
-      {
-         "name": "Windows gradle_fast_start_test",
-         "repo": "flutter",
-         "task_name": "win_gradle_fast_start_test",
-         "flaky": false
-      },
       {
          "name": "Windows gradle_jetifier_test",
          "repo": "flutter",

dev/try_builders.json

@@ -63,13 +63,6 @@
          "task_name":"linux_fuchsia_precache",
          "enabled":true
       },
-      {
-         "name":"Linux gradle_fast_start_test",
-         "repo":"flutter",
-         "task_name":"linux_gradle_fast_start_test",
-         "enabled":true,
-         "run_if": ["dev/**", "bin/**"]
-      },
       {
          "name":"Linux gradle_jetifier_test",
          "repo":"flutter",
@@ -214,13 +207,6 @@
          "enabled":true,
          "run_if":["dev/**", "packages/flutter/**", "packages/flutter_goldens/**", "packages/flutter_goldens_client/**", "packages/flutter_test/**", "packages/flutter_tools/lib/src/test/**", "bin/**"]
       },
-      {
-         "name":"Mac gradle_fast_start_test",
-         "repo":"flutter",
-         "task_name":"mac_gradle_fast_start_test",
-         "enabled":true,
-         "run_if":["dev/**", "bin/**"]
-      },
       {
          "name":"Mac gradle_jetifier_test",
          "repo":"flutter",
@@ -345,13 +331,6 @@
          "enabled":true,
          "run_if":["dev/", "packages/flutter/", "packages/flutter_test/", "packages/flutter_goldens/", "packages/flutter_tools/lib/src/test/", "bin/"]
       },
-      {
-         "name": "Windows gradle_fast_start_test",
-         "repo": "flutter",
-         "task_name": "win_gradle_fast_start_test",
-         "enabled":true,
-         "run_if":["dev/**", "bin/**"]
-      },
       {
          "name": "Windows gradle_jetifier_test",
          "repo": "flutter",