Update Ruby status to completed in README (#236)

Author: donald-pinckney

README.md

@@ -40,5 +40,5 @@ Appropriately adjust the installation directory based on your coding agent.
 - [x] Go ✅
 - [x] Java ✅
 - [x] .NET ✅
-- [ ] Ruby 🚧 ([PR](https://github.com/temporalio/skill-temporal-developer/pull/41))
+- [x] Ruby ✅
 - [ ] PHP 🚧 ([PR](https://github.com/temporalio/skill-temporal-developer/pull/40))