api/twitter: don't return thumb for photos in a picker

it's the same image anyway, this just makes the response smaller

api/src/processing/services/twitter.js

@@ -180,7 +180,6 @@ export default async function({ id, index, toGif, dispatcher }) {
                     return {
                         type: "photo",
                         url,
-                        thumb: url,
                     }
                 }