[Bug] Choice Component - Dash placeholder appears in required radio buttons

## Summary
A dash "—" option recently appeared as the first selectable item in required **Choice** radio button components. This option represents a "no value chosen" state but should not be visible when the component is configured as **Required**, since a required field must have a value selected. This doesn't affect validation, but it wasn't like this before.

**Severity: Medium**

## Steps to Reproduce
1. Open any screen containing a **Choice** component configured with **radio buttons** and **Required**.
2. Ensure the component has a non-empty data source (e.g., a table, a relation or lookup).
3. Observe the first row in the list.

## Current Behavior
A dash "—" appears as the first selectable option in the radio button list of a **Required** choice component.

## Expected Behavior
For **Required** choice components using **radio buttons**, the dropdown should show directly just the list of valid values with no placeholder or "no selection" row. The dash option should only appear (if at all) for **non-required** fields where an empty selection is semantically valid.

## Screenshots/Evidence

## Size Estimate
- [x] Small
- [ ] Medium
- [ ] Large