chore(roadmap): update to readme to point to correct location of roadmap (aws#30460)

### Issue # (if applicable)

N/A

### Reason for this change

The README.md currently points to a roadmap that is no longer in use. 

### Description of changes

Removing old roadmap reference and pointing to the proper roadmap location.

### 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)

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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: adamjkeller

README.md

@@ -140,7 +140,7 @@ You may also find help on these community resources:
 
 ## Roadmap
 
-The [AWS CDK Roadmap project board](https://github.com/orgs/aws/projects/7) lets developers know about our upcoming features and priorities to help them plan how to best leverage the CDK and identify opportunities to contribute to the project. See [ROADMAP.md](https://github.com/aws/aws-cdk/blob/main/ROADMAP.md) for more information and FAQs.
+The AWS CDK Roadmap lets developers know about our upcoming features and priorities to help them plan how to best leverage the CDK and identify opportunities to contribute to the project. See [ROADMAP.md](https://github.com/aws/aws-cdk/blob/main/ROADMAP.md) for more information and FAQs.
 
 ## Contributing