Always log missing official build attribute

[smoogipoo]

This is normally "logged" (via a notification) here:

osu/osu.Game/Updater/UpdateManager.cs

Lines 52 to 60 in 3d6a9cc

	if (game.IsDeployedBuild && version != lastVersion)
	{
	// only show a notification if we've previously saved a version to the config file (ie. not the first run).
	if (!string.IsNullOrEmpty(lastVersion))
	Notifications.Post(new UpdateCompleteNotification(version));
	if (RuntimeInfo.EntryAssembly.GetCustomAttribute<OfficialBuildAttribute>() == null)
	Notifications.Post(new SimpleNotification { Text = NotificationsStrings.NotOfficialBuild });
	}

... but this only happens once on a new version of the game. In particular, it makes it difficult for us developers to understand what went wrong. This should help with figuring out the appropriate response to re-occurrences of #28556.

I also don't particularly care about translations here, only that the text is the same as the other case.