docs: update PUBSUB.md (#3880)

last code wasn't working on line 56. Instead of converting Uint8array to String it was converting the array to string. So instead of text as output , it shows array but with type string. Fixed now with TextDecoder. Working perfectly.

Co-authored-by: Alex Potsides <alex@achingbrain.net>

Author: vilgacx

docs/core-api/PUBSUB.md

@@ -53,7 +53,7 @@ An optional object which may have the following keys:
 
 ```JavaScript
 const topic = 'fruit-of-the-day'
-const receiveMsg = (msg) => console.log(msg.data.toString())
+const receiveMsg = (msg) => console.log(new TextDecoder().decode(msg.data))
 
 await ipfs.pubsub.subscribe(topic, receiveMsg)
 console.log(`subscribed to ${topic}`)
@@ -203,4 +203,4 @@ console.log(peerIds)
 A great source of [examples][] can be found in the tests for this API.
 
 [examples]: https://github.com/ipfs/js-ipfs/blob/master/packages/interface-ipfs-core/src/pubsub
-[AbortSignal]: https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal
+[AbortSignal]: https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal