Change contentTopic to string (#463)

* Change contentTopic to string

* Missed a spot

* Try to fix Windows CI

Co-authored-by: Oskar Thorén <ot@oskarthoren.com>

examples/v2/basic2.nim

@@ -35,7 +35,7 @@ proc runBackground() {.async.} =
 
   # Publish to a topic
   let payload = cast[seq[byte]]("hello world")
-  let message = WakuMessage(payload: payload, contentTopic: ContentTopic(1))
+  let message = WakuMessage(payload: payload, contentTopic: ContentTopic("/waku/2/default-content/proto"))
   await node.publish(topic, message)
 
 # TODO Await with try/except here

examples/v2/chat2.nim

@@ -36,8 +36,7 @@ const
   PayloadV1* {.booldefine.} = false
   DefaultTopic = "/waku/2/default-waku/proto"
 
-  Dingpu = "dingpu".toBytes
-  DefaultContentTopic = ContentTopic(uint32.fromBytes(Dingpu))
+  DefaultContentTopic = ContentTopic("dingpu")
 
 # XXX Connected is a bit annoying, because incoming connections don't trigger state change
 # Could poll connection pool or something here, I suppose