Typo `namespace` should be `broker`

[nathanclevenger]

Which Cloudflare product does this pertain to?

Pub/Sub

Existing documentation URL(s)

https://developers.cloudflare.com/pub-sub/get-started/guide/#5-create-a-broker

Section that requires update

5. Create a Broker

What needs to change?

$ wrangler pubsub namespace create example-broker --namespace=my-namespace

How should it change?

$ wrangler pubsub broker create example-broker --namespace=my-namespace

Additional information

No response