[Language] Liberated cities should be named "Independent", not "Rebels"

When I voluntarily liberate a city to become its own Independent People, the culture of that city is named "Rebels from the {Culture}" (e.g., "Rebels from the Umayyads").  This is probably because the same language term is used when actual rebel units are generated from low stability.

Proposal: When I voluntarily liberate a city, the newly independent city's culture should become "Independent {Culture}" instead of "Rebels from the {Culture}".  E.g., "Independent Umayyads" or "Independent British".