Fix aria-labelledby-prop on MultiSelect

Parts of the MultiSelect is still using a prefixed ID for the aria-labelledby attribute – even though a custom aria-labelledby ID is provided.

This causes aXe to complain about missing referenced elements.

Expectation: When providing a custom aria-labelledby ID, the component should use this instead of a prefixed version based on the ID-prop.

Actual Result: The hidden value input uses a prefixed aria-labelledby ID. The aria-labelledby ID is also applied twice on the control element.