docs(aws-cognito): fix link to aws-cognito-identitypool-alpha module (#19306)

fixes #19291


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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: corymhall

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

@@ -31,7 +31,7 @@ The two main components of Amazon Cognito are [user
 pools](https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-user-identity-pools.html) and [identity
 pools](https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-identity.html). User pools are user directories
 that provide sign-up and sign-in options for your app users. Identity pools enable you to grant your users access to
-other AWS services. Identity Pool L2 Constructs can be found [here](../aws-cognito-identitypool).
+other AWS services. Identity Pool L2 Constructs can be found [here](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cognito-identitypool-alpha-readme.html).
 
 This module is part of the [AWS Cloud Development Kit](https://github.com/aws/aws-cdk) project.