Delete simulator after plugin_test_ios (#136265)

Remove simulator once it's no longer needed for test `plugin_test_ios` .

Fixes https://github.com/flutter/flutter/issues/136224

dev/devicelab/lib/tasks/plugin_tests.dart

@@ -263,7 +263,10 @@ public class $pluginClass: NSObject, FlutterPlugin {
           throw TaskResult.failure('Platform unit tests failed');
         }
       case 'ios':
+        String? simulatorDeviceId;
+        try {
           await testWithNewIOSSimulator('TestNativeUnitTests', (String deviceId) async {
+            simulatorDeviceId = deviceId;
             if (!await runXcodeTests(
               platformDirectory: path.join(rootPath, 'ios'),
               destination: 'id=$deviceId',
@@ -274,6 +277,9 @@ public class $pluginClass: NSObject, FlutterPlugin {
               throw TaskResult.failure('Platform unit tests failed');
             }
           });
+        } finally {
+          await removeIOSimulator(simulatorDeviceId);
+        }
       case 'linux':
         if (await exec(
           path.join(rootPath, 'build', 'linux', 'x64', 'release', 'plugins', 'plugintest', 'plugintest_test'),