TraitsInfos.xml in the Civilizations folder, remember to make a backup copy of the original, or put the modified copy in the customassets folder.
Note if you are playing BTS, the File will be within the Warlords directory (Warlords/Assets/XML/Civilizations/TraitInfos.xml). BTS didnt actually change anything with the file, so it wasnt included. Warlords has the most recent changes.