The "required" prop is not working on Dropdown

[stripp915]

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Current behavior
Using the 'required' attribute on a Dropdown component does not prevent a form from submitting, even when the dropdown value is empty.

Expected behavior
Either the 'required' attribute affects a form's validity, or the attribute is removed from this component.

This appears to have been removed on this commit: 5f2096e

The props still contain a 'required' attribute, but all references to that prop were removed from the rest of the component.