style(api): remove whitespace

Author: Jiankai Zheng

src/main/java/spotify/api/impl/ArtistApiRetrofit.java

@@ -135,7 +135,6 @@ public ArtistFullCollection getRelatedArtists(String artistId) {
 
     @Override
     public ArtistFullCollection getArtists(List<String> listOfArtistIds) {
-
         String artistIdsWithCommaDelimiter = String.join(",", listOfArtistIds);
 
         logger.trace("Constructing HTTP call to fetch multiple artists.");