feat: refactor HipHopArtist class and remove unused artist classes and tests

Author: bryanasb251

lesson_16/objects/objects_app/src/main/java/com/codedifferently/lesson16/hiphopArtist/DMX.java

@@ -36,14 +36,15 @@ public void addAlbum(String album) {
     System.out.println(album + " was added to " + stageName + "'s discography.");
   }
 
-  public void listAlbums() throws NoAlbumsException {
+  public String listAlbums() throws NoAlbumsException {
     if (albums.isEmpty()) {
       throw new NoAlbumsException(stageName + " has no albums listed.");
     }
     System.out.println("Albums by " + stageName + ":");
     for (String album : albums) {
       System.out.println("- " + album);
     }
+    return stageName;
   }
 
   public String getBio() {