[FR] Note Amazon Q Developer rebrand and refresh pinned deps (aws-cdk-lib 2.31.0, boto3 1.23.10)

## Use case
New visitors landing here in 2026 hit two friction points: the product was rebranded to Amazon Q Developer (April 2024), and `python/requirements.txt` pins `aws-cdk-lib==2.31.0` (June 2022) and `boto3==1.23.10` (May 2022), which fail against current CDK CLI.

## Proposal
1. Add a top-of-README note: "Amazon CodeWhisperer is now part of Amazon Q Developer" with a link.
2. Loosen pins in `python/requirements.txt` to `aws-cdk-lib>=2.100,<3`, `boto3>=1.34`, or bump to current tested versions.

## Existing art
Several aws-samples workshop repos carry an Amazon Q rebrand banner.

## Not a bug
Workshop still synthesizes; this is UX + supply-chain freshness.

Thanks for maintaining aws-samples/amazon-codewhisperer-workshop!

Start with the top-level README and python/requirements.txt, checking the existing product wording and pinned aws-cdk-lib and boto3 versions. Run the workshop synthesis with the refreshed dependencies; done means the README includes the Amazon Q Developer rebrand note and link, and the dependency versions work with the current CDK CLI.

Written by the indexing model from the issue text.