Update src/app/ReadClient.h

Co-authored-by: Boris Zbarsky <bzbarsky@apple.com>

src/app/ReadClient.h

@@ -329,7 +329,7 @@ class ReadClient : public Messaging::ExchangeDelegate
      *  When subscribing to ICD and liveness timeout reached, the read client will move to the `InactiveICDSubscription` state and
      * resubscription can be triggered via OnActiveModeNotification().
      *
-     *  If the subscription is not in the`InactiveICDSubscription` state, this function will do nothing. So it is always safe to
+     *  If the subscription is not in the `InactiveICDSubscription` state, this function will do nothing. So it is always safe to
      * call this function when a check-in message is received.
      */
     void OnActiveModeNotification();