Update articles/qos_deadline_liveliness_lifespan.md

Co-Authored-By: William Woodall <william+github@osrfoundation.org>

articles/qos_deadline_liveliness_lifespan.md

@@ -94,7 +94,7 @@ Both of these fall under a category of "Resource Status Events".
 
 To handle these notifications, new callback functions can be provided by the user that will be called any time an event occurs for a particular Topic.
 It will receive as a parameter a struct value that contains the information about the event such as when the event took place and other metadata related to the event.
-These callback functions would be optionally provided by the user's application when it calls the create function for publishers and subscribers.
+These callback functions would be optionally provided by the user's application when it calls the create function for publishers and subscriptions.
 The constructors and create functions will be overloaded to make this new handler optional.
 
 The status event handlers will not be called once for every status event.