Remove unused flutter_gallery_instrumentation_test (#86812)

dev/devicelab/bin/tasks/flutter_gallery_instrumentation_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 'dart:io';
-
-import 'package:flutter_devicelab/framework/devices.dart';
-import 'package:flutter_devicelab/framework/framework.dart';
-import 'package:flutter_devicelab/framework/task_result.dart';
-import 'package:flutter_devicelab/framework/utils.dart';
-
-// This test runs "//dev/integration_tests/flutter_gallery/test/live_smoketest.dart", which communicates
-// with the Java code to report its status. If this test fails due to a problem on the Dart
-// side, you can debug that by just running that file directly using `flutter run`.
-
-Future<void> main() async {
-  deviceOperatingSystem = DeviceOperatingSystem.android;
-
-  await task(() async {
-    final Directory galleryDirectory =
-      dir('${flutterDirectory.path}/dev/integration_tests/flutter_gallery');
-    await inDirectory(galleryDirectory, () async {
-      final Device device = await devices.workingDevice;
-      await device.unlock();
-      await flutter('packages', options: <String>['get']);
-      await flutter('clean');
-      await flutter('build', options: <String>['apk', '--target', 'test/live_smoketest.dart']);
-      final String? javaHome = await findJavaHome();
-      final Map<String, String>? environment = javaHome != null
-        ? <String, String>{ 'JAVA_HOME': javaHome }
-        : null;
-      await exec('./tool/run_instrumentation_test.sh', <String>[], environment: environment);
-    });
-
-    return TaskResult.success(null);
-  });
-}