Merge channel header title content for TalkBack

Author: andremion

stream-chat-android-compose/src/main/java/io/getstream/chat/android/compose/ui/messages/header/ChannelHeader.kt

@@ -199,6 +199,7 @@ internal fun DefaultChannelHeaderCenterContent(
                     onClickLabel = onHeaderTitleClickLabel,
                     role = Role.Button,
                 ) { callback(channel) }
+                    .semantics(mergeDescendants = true) {}
             },
         horizontalAlignment = Alignment.CenterHorizontally,
         verticalArrangement = Arrangement.Center,