Update the Seller API to only return the first location

[justintmckibben]

Currently the Sellers endpoint returns an array of locations. However, there are assumptions baked into our code all over the frontend that assumes only one location. We should just amend the API to only return the first location, and ignore the rest.

This would have a parallel change that would need to land at the same time.

sendchinatownlove/sendchinatownlove.github.io#185