Revert "docs: add v2.1.0 upgrade banner and migration guide to v1 README (#310)" (#311)

This reverts commit 6727625.

Author: Devesh-Skyflow

README.md

@@ -1,7 +1,5 @@
 # Skyflow Java
 
-> **Java V2.1.0 IS NOW AVAILABLE:** A new, improved version of the Skyflow SDK is ready with flexible authentication, multi-vault support, builder patterns, and richer error diagnostics. V1 is in maintenance mode (security patches only) and will reach End of Life on October 31, 2026. We recommend upgrading to v2.1.0 — see the **[Migration Guide](docs/migrate_to_v2.md)** for step-by-step instructions.
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 The Skyflow Java SDK is designed to help with integrating Skyflow into a Java backend.
 
 [![CI](https://img.shields.io/static/v1?label=CI&message=passing&color=green?style=plastic&logo=github)](https://github.com/skyflowapi/skyflow-java/actions)