Code reference pages should not show example or explanation area until functionality is ready

[siobhan]

The Example and Explanation functionality will be added once v1.0 of the code reference is out #180

If it isn't difficult to do, it makes sense to hide those sections on the hook, function, and class page template.

(When that functionality is implemented, we may wish to add some sort of call to action to the template that will be displayed whenever there is no example or explanation present)

[Rarst]

Fixed in ​https://github.com/Rarst/wporg-developer/commit/605ac23f341662b1991829127a5fa15c8852fe2b