Fix broken RSC documentation link in Pro docs

The link to react-server-components.md was broken after it was deleted
and its content was merged into major-performance-breakthroughs-upgrade-guide.md
in commit 30a41c1. This updates the link to point to the correct file
which contains all the original RSC content plus additional performance
improvements documentation.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ihabadham

docs/react-on-rails-pro/react-on-rails-pro.md

@@ -22,7 +22,7 @@ See https://www.shakacode.com/react-on-rails-pro/docs/.
 
 ### Pro: React Server Components
 
-See the [announcement here](./react-server-components.md).
+See the [performance breakthroughs guide here](./major-performance-breakthroughs-upgrade-guide.md).
 
 Yes! Big performance gains for the newest React features!