Update RGB sample link (#276)

Author: ConorOkus

docs/case-studies.md

@@ -300,8 +300,8 @@ lastUpdated: false
     <p>A web-first unstoppable bitcoin wallet for everyone</p>
   </div>
   <div class="case-study-item">
-    <a href="https://github.com/RGB-Tools/rgb-lightning-sample" target="_blank"><img src="./assets/github.png" /></a>
-    <h3><a href="https://github.com/RGB-Tools/rgb-lightning-sample" target="_blank">rgb-lightning-sample</a></h3>
+    <a href="https://github.com/RGB-Tools/rgb-lightning-node" target="_blank"><img src="./assets/github.png" /></a>
+    <h3><a href="https://github.com/RGB-Tools/rgb-lightning-node" target="_blank">rgb-lightning-node</a></h3>
     <p>LN node based on ldk-sample supporting RGB assets</p>
   </div>
   <div class="case-study-item">