Goto Settings-> User Interface->Menu Items
2. Search « Discuss ».
3. Tick the box, then in « Actions » choose « Archive »
Then it will be hidden.
If you need it back, in « Filters » of the same window–>Add Custom Filter –> Active –> Is False –>Apply.
Now all the archived items will be shown. Choose the one to be made active by ticking and « Action »–> « Unarchive ».
Refresh your page.