title: CloudWatch log group is not deleted on cdk destroy
body: <p>I have this CDK code:</p>
  <pre><code>const logGroup = new LogGroup(this, 'MyAppLogGroup', {
    logGroupName: 'myapp',
    retention: RetentionDays.ONE_DAY
  });
  </code></pre>
  <p>When I run <code>cdk deploy</code>, log group is created in CloudWatch, but when I run <code>cdk destroy</code>, it's not deleted. Is there some way to enable this?</p>