Fix inaccurate doc comment (#5978)

* Fix inaccurate doc comment

* Add changelog

* amend changelog

Author: morganchen12

FirebaseInAppMessaging/CHANGELOG.md

@@ -1,6 +1,7 @@
-# 2020-07-06 -- v0.22.0
+# 2020-07 -- v0.22.0
 - [changed] Functionally neutral updated import references for dependencies. (#5902)
 - [changed] Updated In-App Messaging to consume the Protobuf-less AB Testing SDK (#5890).
+- [fixed] Fixed an inaccurate doc comment in `InAppMessagingDisplay` (#5972).
 
 # 2020-06-02 -- v0.20.2
 - [fixed] Fixed log message for in-app messaging test on device flow (#5680).

FirebaseInAppMessaging/Sources/Public/FIRInAppMessagingRendering.h

@@ -466,7 +466,7 @@ NS_SWIFT_NAME(InAppMessagingDisplay)
 @protocol FIRInAppMessagingDisplay
 
 /**
- * Method for rendering a specified message on client side. It's called from main thread.
+ * Method for rendering a specified message on client side. Invoked on a background thread.
  * @param messageForDisplay the message object. It would be of one of the three message
  *   types at runtime.
  * @param displayDelegate the callback object used to trigger notifications about certain