Group Plan task sorting shows API error and doesn't save

[saraolson]

1. In the Group view, you should be allowed to sort Group Plan task lists if you have Owner or Manager permissions (even if the task isn't assigned to you)
2. In the Group view, we should block sorting if you are not an Owner or Manager with the error 'You don't have task management permissions.'
3. When on your personal task board view, you should be allowed to sort in any order (but this order does not change anything in the Group view).

Right now, it shows an error 'Use /groups/:groupID/tasks/:taskID/move/to/:position route'

Can reference web for the proper functionality.

[saraolson]

Tested this again, and confirmed it's still happening.

Steps to reproduce:

1. Have an owned Group Plan or a Group Plan you're a manager of
2. Navigate to that task board by tapping the bubble at the top
3. Have a task assigned to someone else
4. Drag and drop that task to reproduce the error