fix websocket playground reference

Author: devalog

fern/products/docs/pages/api-references/api-explorer.mdx

@@ -24,7 +24,7 @@ Allow users to test their calls in a sandbox environment or select the environme
 
 <div style="position: relative; padding-bottom: 50.63657407407407%; height: 0;"><iframe src="https://www.loom.com/embed/cb642161678e41cabcb677b900006f40?sid=5e45243c-3ba1-45cf-860b-72eee1970fc5?hide_owner=true&hide_share=true&hide_title=true&hideEmbedTopBar=true" frameborder="0" webkitallowfullscreen mozallowfullscreen allowfullscreen style="position: absolute; top: 0; left: 0; width: 100%; height: 100%;"></iframe></div>
 
-### WebSocket playground
+### WebSocket Playground
 
 For APIs that support WebSocket connections, the API Explorer includes a **WebSocket**-specific Playground. The WebSocket Playground also allows users to establish a connection with the API, and send/receive messages in real-time.