feat(cognito): the Cognito Identity Pools module is now in Developer Preview (#31854)

### Description of changes

Updated the README stability banner as we move Cognito Identity Pools into developer preview, taking the next step towards being fully stabilized.

### Checklist
- [x] My code adheres to the [CONTRIBUTING GUIDE](https://github.com/aws/aws-cdk/blob/main/CONTRIBUTING.md) and [DESIGN GUIDELINES](https://github.com/aws/aws-cdk/blob/main/docs/DESIGN_GUIDELINES.md)

----

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

Author: Leo10Gama

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

@@ -1,25 +1,25 @@
 # Amazon Cognito Identity Pool Construct Library
-
-> **Identity Pools are in a separate module while the API is being stabilized. Once we stabilize the module, they will**
-**be included into the stable [aws-cognito](../aws-cognito) library. Please provide feedback on this experience by**
-**creating an [issue here](https://github.com/aws/aws-cdk/issues/new/choose)**
-
 <!--BEGIN STABILITY BANNER-->
 
 ---
 
-![cdk-constructs: Experimental](https://img.shields.io/badge/cdk--constructs-experimental-important.svg?style=for-the-badge)
+![cdk-constructs: Developer Preview](https://img.shields.io/badge/cdk--constructs-developer--preview-informational.svg?style=for-the-badge)
 
-> The APIs of higher level constructs in this module are experimental and under active development.
-> They are subject to non-backward compatible changes or removal in any future version. These are
-> not subject to the [Semantic Versioning](https://semver.org/) model and breaking changes will be
-> announced in the release notes. This means that while you may use them, you may need to update
-> your source code when upgrading to a newer version of this package.
+> The APIs of higher level constructs in this module are in **developer preview** before they
+> become stable. We will only make breaking changes to address unforeseen API issues. Therefore,
+> these APIs are not subject to [Semantic Versioning](https://semver.org/), and breaking changes
+> will be announced in release notes. This means that while you may use them, you may need to
+> update your source code when upgrading to a newer version of this package.
 
 ---
 
 <!--END STABILITY BANNER-->
 
+
+> **Identity Pools are in a separate module while the API is being stabilized. Once we stabilize the module, they will**
+**be included into the stable [aws-cognito](../aws-cognito) library. Please provide feedback on this experience by**
+**creating an [issue here](https://github.com/aws/aws-cdk/issues/new/choose)**
+
 [Amazon Cognito Identity Pools](https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-identity.html) enable you to grant your users access to other AWS services.
 
 Identity Pools are one of the two main components of [Amazon Cognito](https://docs.aws.amazon.com/cognito/latest/developerguide/what-is-amazon-cognito.html), which provides authentication, authorization, and

packages/@aws-cdk/aws-cognito-identitypool-alpha/package.json

@@ -99,7 +99,7 @@
     "node": ">= 14.15.0"
   },
   "stability": "experimental",
-  "maturity": "experimental",
+  "maturity": "developer-preview",
   "awscdkio": {
     "announce": false
   },