Perform Show() at the bottom of the method

Probably not affecting behaviour, but makes more sense.

osu.Game/Overlays/ChatOverlay.cs

@@ -313,8 +313,6 @@ namespace osu.Game.Overlays
         /// <param name="channel">The channel containing the message.</param>
         public void HighlightMessage(Message message, Channel channel)
         {
-            Show();
-
             Debug.Assert(channel.Id == message.ChannelId);
 
             if (currentChannel.Value?.Id != channel.Id)
@@ -326,6 +324,8 @@ namespace osu.Game.Overlays
             }
 
             channel.HighlightedMessage.Value = message;
+
+            Show();
         }
 
         private float startDragChatHeight;