Update README to reflect Minecraft version 1.21.4

The gradle.properties was already configured for version 1.21.4, but the README badge still showed 1.20.6. Updated the version badge to correctly display 1.21.4.

Author: claude

README.md

@@ -8,7 +8,7 @@
   <a href="https://anticope.ml/pages/MeteorAddons.html"><img src="https://img.shields.io/badge/Verified%20Addon-Yes-blueviolet" alt="Verified Addon"></a>
   <a href="https://github.com/AntiCope/meteor-rejects/releases"><img src="https://img.shields.io/badge/Version-v0.1-orange" alt="Version"></a>
   <img src="https://img.shields.io/badge/spaghetti%20code-yes-success?logo=java" alt="Spagetti code: yes">
-  <img src="https://img.shields.io/badge/Minecraft%20Version-1.20.6-blue" alt="Minecraft Version">
+  <img src="https://img.shields.io/badge/Minecraft%20Version-1.21.4-blue" alt="Minecraft Version">
   <a href="https://github.com/AntiCope/meteor-rejects/commits/master"><img src="https://img.shields.io/github/last-commit/AntiCope/meteor-rejects?logo=git" alt="Last commit"></a>
   <img src="https://img.shields.io/github/workflow/status/AntiCope/meteor-rejects/Java%20CI%20with%20Gradle?logo=github" alt="build status">
   <img src="https://img.shields.io/github/languages/code-size/AntiCope/meteor-rejects" alt="Code Size">