Format example code in 'Publishing (Sending Messages)' section of ref doc.

Closed #2533

src/main/asciidoc/reference/redis-messaging.adoc

@@ -22,7 +22,9 @@ To publish a message, you can use, as with the other operations, either the low-
 // send message through connection RedisConnection con = ...
 byte[] msg = ...
 byte[] channel = ...
-con.publish(msg, channel); // send message through RedisTemplate
+con.publish(msg, channel);
+
+// send message through RedisTemplate
 RedisTemplate template = ...
 template.convertAndSend("hello!", "world");
 ----