chore: remove preview from README.md (#459)

Author: yonib05

README.md

@@ -195,8 +195,3 @@ This project is licensed under the Apache License 2.0 - see the [LICENSE](LICENS
 
 See [CONTRIBUTING](CONTRIBUTING.md#security-issue-notifications) for more information.
 
-## ⚠️ Preview Status
-
-Strands Agents is currently in public preview. During this period:
-- APIs may change as we refine the SDK
-- We welcome feedback and contributions