adm1 Liberia missing ISO 3166-2 codes for Gbapolu, River Gee counties

[MLWorley]

In ne_10m_admin_1_states_provinces, all the counties of Liberia are present, but 2 of them are missing their ISO 3166-2 values.

adm1_code = LBR-1458, name = 'River Gee', should have iso_3166_2 = 'LR-RG'

adm1_code = LBR-1459, name = 'Gbapolu', should have iso_3166_2 = 'LR-GP' (ISO uses the alternate name 'Gbarpolu' if that would help)