Fix Southern Luri autonym

Fix Southern Luri autonym

Received as feedback from Southern Luri community:
"Dumeni" means "Under" (Southern)

Also removing Northern Luri from the fallback list.
Southern Luri speekers can't understand Northern Luri,
but everyone in the region can understand Persian
(official language in the region).

Follow-up to I68154c19880ee59da05493fb72e735e61c3183aa
Follow-up to I1099cb846f029df850126e59306849b0eec88e7b
Follow-up to I3cc17d61c6f99b42f6befb39a4c1d6544558cd7e

Change-Id: Iaa1d3da94261f23a2e7b6f488ebfcce5cf457413