chore: provide a link to the Gen2 migration tool in Gen2 banner (#14533)

* Update migration guidance for Gen 1 customers

Encourage Gen 1 customers to test migration tool for Gen 2.

* Revise migration instructions for Gen 1 customers

Updated wording for migration guidance from Gen 1 to Gen 2.

Author: iliapolo

Readme.md

@@ -23,9 +23,9 @@
 >
 > If you are starting a new project, we recommend starting with [Amplify Gen 2](https://github.com/aws-amplify/amplify-backend).
 >
-> If you are an existing Gen 1 customer, we recommend that you continue working with your Gen 1 Amplify project. We are actively developing migration tooling to aid in transitioning your project from Gen 1 to Gen 2. We remain committed to supporting both Gen 1 and Gen 2 for the foreseeable future.
->
-> Customers on Gen 1 will continue to receive support for high-priority bugs and essential security updates.
+> If you are an existing Gen 1 customer, we encourage you to start planning your migration to Gen 2 by
+> testing the [beta version of our migration tool](https://github.com/aws-amplify/amplify-cli/discussions/14490)
+> on **non-production** environments. We remain committed to supporting both Gen 1 and Gen 2 for the foreseeable future.
 
 # AWS Amplify CLI (Gen 1)