Form questions cannot be moved into a repeating set

## Description
When a user tries to move a question from outside a repeating set to inside of one, they cannot.

## Steps to reproduce
1. Sign-in
2. Open a form with a repeating set and dropdown
3. Try to move the dropdown from outside the repeating set, to inside the question

## Details
- **Browser**: Chrome
- **Operating system**: Mac
- **Environment**: Production
- **Language**: English, French
- **Viewport**: any screen size

## Expected behaviour
1. Clients can move any question from outside of a repeating set to inside of the set with the "move up", "move down", or by dragging the set in the "pages" view.
2. Clients can move any question from inside of a repeating set to outside of the set with the same actions.

## Screenshots or videos
State 1

Click "move up". Set jumps ahead, but does not go into the repeating set.