Un-marks an achievement for tracking in the WatchFrame.
- Number - ID of the achievement to add to tracking.
- A maximum of WATCHFRAME_MAXACHIEVEMENTS (10 as of 5.4.8) tracked achievements can be displayed by the WatchFrame at a time.
- You may need to manually updated the AchievementUI and WatchFrame after calling this function.
Patch 3.1.0 (2009-04-14): Added.