Doc update about ruby version 3.0+ (mastodon#29202)

README.md

@@ -69,7 +69,7 @@ Mastodon acts as an OAuth2 provider, so 3rd party apps can use the REST and Stre
 
 - **PostgreSQL** 12+
 - **Redis** 4+
-- **Ruby** 2.7+
+- **Ruby** 3.0+
 - **Node.js** 16+
 
 The repository includes deployment configurations for **Docker and docker-compose** as well as specific platforms like **Heroku**, **Scalingo**, and **Nanobox**. For Helm charts, reference the [mastodon/chart repository](https://github.com/mastodon/chart). The [**standalone** installation guide](https://docs.joinmastodon.org/admin/install/) is available in the documentation.