Update CI badge in README (#42394)

This PR updates the CI badge in the README, after the CI workflow
reorganization.

Release Notes:

- N/A

README.md

@@ -1,7 +1,7 @@
 # Zed
 
 [![Zed](https://img.shields.io/endpoint?url=https://raw.githubusercontent.com/zed-industries/zed/main/assets/badge/v0.json)](https://zed.dev)
-[![CI](https://github.com/zed-industries/zed/actions/workflows/ci.yml/badge.svg)](https://github.com/zed-industries/zed/actions/workflows/ci.yml)
+[![CI](https://github.com/zed-industries/zed/actions/workflows/run_tests.yml/badge.svg)](https://github.com/zed-industries/zed/actions/workflows/run_tests.yml)
 
 Welcome to Zed, a high-performance, multiplayer code editor from the creators of [Atom](https://github.com/atom/atom) and [Tree-sitter](https://github.com/tree-sitter/tree-sitter).