[AuthModal] Remove unused option.
[AuthModal] Remove unused option.

https://github.com/artsy/force/pull/153/files#diff-dd71c83f0984aa16d35337c4a60e59faL35

anandaroop/force,yuki24/force,joeyAghion/force,cavvia/force-1,mzikherman/force,cavvia/force-1,damassi/force,oxaudo/force,artsy/force-public,erikdstock/force,izakp/force,izakp/force,xtina-starr/force,artsy/force,damassi/force,damassi/force,eessex/force,kanaabe/force,oxaudo/force,izakp/force,eessex/force,xtina-starr/force,artsy/force,oxaudo/force,anandaroop/force,xtina-starr/force,kanaabe/force,erikdstock/force,oxaudo/force,artsy/force-public,joeyAghion/force,erikdstock/force,damassi/force,cavvia/force-1,yuki24/force,mzikherman/force,anandaroop/force,eessex/force,cavvia/force-1,erikdstock/force,kanaabe/force,kanaabe/force,eessex/force,mzikherman/force,joeyAghion/force,kanaabe/force,xtina-starr/force,artsy/force,izakp/force,mzikherman/force,anandaroop/force,artsy/force,joeyAghion/force,yuki24/force,yuki24/force