Remove unused flag `--target-platform` from `flutter run` (#34369)

packages/flutter_tools/lib/src/commands/run.dart

@@ -55,12 +55,7 @@ abstract class RunCommandBase extends FlutterCommand with DeviceBasedDevelopment
               'to precompile some code by the offline compiler. '
               'This flag is only allowed when running as --dynamic --profile (recommended) or '
               '--debug (may include unwanted debug symbols).',
-      )
-      ..addOption('target-platform',
-        defaultsTo: 'default',
-        allowed: <String>['default', 'android-arm', 'android-arm64', 'android-x86', 'android-x64'],
-        help: 'Specify the target platform when building the app for an '
-              'Android device.\nIgnored on iOS.');
+      );
     usesTargetOption();
     usesPortOptions();
     usesIpv6Flag();