possible react-native-deck-swiper fork cleanup

[lcjohnso]

The https://github.com/zooniverse/react-native-deck-swiper fork is no longer in use (since #458), and the repo for the fork has been archived. A more recent, up-to-date version of the library is now in use, but there are two references to the library that may no longer be needed (maybe referring to older versions of the package?):

1. https://github.com/zooniverse/mobile/blob/master/package.json#L20-L22
2. https://github.com/zooniverse/mobile/blob/master/rn-cli.config.js#L7

There are no known issues associated with this code, but wanted to issue up a check as part of close-out activities for the old fork.