docs(autoscaling): correct feature flag for launch templates (#27235)

The docs for [`AutoScalingGroup`](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_autoscaling-readme.html#auto-scaling-group) mention using the feature flag `@aws-cdk/aws-autoscaling:disableDefaultLaunchConfigCreation` in order to generate launch templates instead of launch configs.

This flag doesn't exist and the correct flag should be `@aws-cdk/aws-autoscaling:generateLaunchTemplateInsteadOfLaunchConfig` as specified on the [feature flags page](https://github.com/aws/aws-cdk/blob/main/packages/%40aws-cdk/cx-api/FEATURE_FLAGS.md#aws-cdkaws-autoscalinggeneratelaunchtemplateinsteadoflaunchconfig)

_Was raised by Carl Fürstenberg on the #aws-cdk  slack channel_

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*By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license*

Author: iRoachie

packages/aws-cdk-lib/aws-autoscaling/README.md

@@ -23,7 +23,7 @@ new autoscaling.AutoScalingGroup(this, 'ASG', {
 });
 ```
 
-Creating an `AutoScalingGroup` from a Launch Configuration has been deprecated. All new accounts created after December 31, 2023 will no longer be able to create Launch Configurations. With the `@aws-cdk/aws-autoscaling:disableDefaultLaunchConfigCreation` feature flag set to true, `AutoScalingGroup` properties used to create a Launch Configuration will now be used to create a `LaunchTemplate` using a [Launch Configuration to `LaunchTemplate` mapping](https://docs.aws.amazon.com/autoscaling/ec2/userguide/migrate-launch-configurations-with-cloudformation.html#launch-configuration-mapping-reference). Specifically, the following `AutoScalingGroup` properties will be used to generate a `LaunchTemplate`:
+Creating an `AutoScalingGroup` from a Launch Configuration has been deprecated. All new accounts created after December 31, 2023 will no longer be able to create Launch Configurations. With the `@aws-cdk/aws-autoscaling:generateLaunchTemplateInsteadOfLaunchConfig` feature flag set to true, `AutoScalingGroup` properties used to create a Launch Configuration will now be used to create a `LaunchTemplate` using a [Launch Configuration to `LaunchTemplate` mapping](https://docs.aws.amazon.com/autoscaling/ec2/userguide/migrate-launch-configurations-with-cloudformation.html#launch-configuration-mapping-reference). Specifically, the following `AutoScalingGroup` properties will be used to generate a `LaunchTemplate`:
 * machineImage
 * keyName
 * instanceType