docs: Close paren on TaskDeveloper code snippet

Someone might want to copypasta this and then would get an error.

I am sure I don't know anyone who would just go around
copypasta-ing the docs. But if they did, is all I am saying.

*whistling*

Testing Done:
Published the docs and gave an eyeball.

Reviewed at https://rbcommons.com/s/twitter/r/809/