[flutter_tools] delete flutter format command (#129360)

On the current stable branch (3.10.x), `flutter format` no longer works, and gives an error. This change just deletes the code.

Fixes https://github.com/flutter/flutter/issues/115809

packages/flutter_tools/lib/executable.dart

@@ -28,7 +28,6 @@ import 'src/commands/doctor.dart';
 import 'src/commands/downgrade.dart';
 import 'src/commands/drive.dart';
 import 'src/commands/emulators.dart';
-import 'src/commands/format.dart';
 import 'src/commands/generate.dart';
 import 'src/commands/generate_localizations.dart';
 import 'src/commands/ide_config.dart';
@@ -200,7 +199,6 @@ List<FlutterCommand> generateCommands({
     signals: globals.signals,
   ),
   EmulatorsCommand(),
-  FormatCommand(),
   GenerateCommand(),
   GenerateLocalizationsCommand(
     fileSystem: globals.fs,

packages/flutter_tools/lib/src/commands/format.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:args/args.dart';
-
-import '../base/common.dart';
-import '../runner/flutter_command.dart';
-
-class FormatCommand extends FlutterCommand {
-  FormatCommand();
-
-  @override
-  ArgParser argParser = ArgParser.allowAnything();
-
-  @override
-  final String name = 'format';
-
-  @override
-  List<String> get aliases => const <String>['dartfmt'];
-
-  @override
-  String get description => deprecationWarning;
-
-  @override
-  final bool hidden = true;
-
-  @override
-  String get deprecationWarning {
-    return 'The "format" command is deprecated. Please use the "dart format" '
-           'sub-command instead, which has the same command-line usage as '
-           '"flutter format".\n';
-  }
-
-  @override
-  Future<FlutterCommandResult> runCommand() async {
-    throwToolExit(deprecationWarning);
-  }
-}