Update spec/mercure.md

Co-authored-by: Antoine Bluchet <[email protected]>

spec/mercure.md

@@ -31,7 +31,7 @@ Mercure provides a common publish-subscribe mechanism for public and private web
 Mercure enables the pushing of any web content to web browsers and other clients in
 a fast, reliable and battery-efficient way. It is especially useful for publishing real-time updates
 of resources served through sites and web APIs to web and mobile apps and can also be used
-as a simple publish subcribe system.
+as a simple publish-subscribe system.
 
 Subscription requests are relayed through hubs, which validate and verify the request.
 When new or updated content becomes available, hubs check if subscribers are authorized to receive it