chore(aws-cdk-readme): replace deprecated method used in aws-chatbot …

…README.md (#13521)

Currently addLambdaInvokeCommandPermissions method used to get the permissions,
which is a deprecated method now.
Use addToPolicy method to get necessary permissions

fix: #13444

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packages/@aws-cdk/aws-chatbot/README.md

@@ -34,11 +34,6 @@ const slackChannel = new chatbot.SlackChannelConfiguration(this, 'MySlackChannel
  slackChannelId: 'YOUR_SLACK_CHANNEL_ID',
 });
 
-slackChannel.addLambdaInvokeCommandPermissions();
-slackChannel.addNotificationPermissions();
-slackChannel.addSupportCommandPermissions();
-slackChannel.addReadOnlyCommandPermissions();
-
 slackChannel.addToPrincipalPolicy(new iam.PolicyStatement({
  effect: iam.Effect.ALLOW,
  actions: [