Add comment to second example about body

Explain that by providing null/undefined, we are telling it we are not sending a body(or specifically a lack there of)

snippets/httpPost.md

@@ -42,7 +42,7 @@ Logs: {
 */
 httpPost(
   'https://jsonplaceholder.typicode.com/posts',
-  null,
+  null, //does not send a body
   console.log
 ); /*
 Logs: {