fix: typo in server-url/events.mdx (VapiAI#140)

Author: sharnie

server-url/events.mdx

@@ -82,7 +82,7 @@ Or if it's an object:
 The result will be appended to the conversation, and the assistant will decide what to do with the response based on its system prompt.
 
 <Note>
-  If you don't need to return a response, you can use the `async: true` parameter in your assitant's
+  If you don't need to return a response, you can use the `async: true` parameter in your assistant's
   function configuration. This will prevent the assistant from waiting for a response from your
   server.
 </Note>