remove sort option: Oldest

lib/ui/collections_gallery_widget.dart

@@ -120,9 +120,6 @@ class _CollectionsGalleryWidgetState extends State<CollectionsGalleryWidget>
         } else if (sortKey == AlbumSortKey.newestPhoto) {
           return second.thumbnail.creationTime
               .compareTo(first.thumbnail.creationTime);
-        } else if (sortKey == AlbumSortKey.oldestPhoto) {
-          return first.thumbnail.creationTime
-              .compareTo(second.thumbnail.creationTime);
         } else {
           return second.collection.updationTime
               .compareTo(first.collection.updationTime);
@@ -407,9 +404,6 @@ class _CollectionsGalleryWidgetState extends State<CollectionsGalleryWidget>
         case AlbumSortKey.newestPhoto:
           text = "Newest";
           break;
-        case AlbumSortKey.oldestPhoto:
-          text = "Oldest";
-          break;
         case AlbumSortKey.lastUpdated:
           text = "Last updated";
       }

lib/utils/local_settings.dart

@@ -3,7 +3,6 @@ import 'package:shared_preferences/shared_preferences.dart';
 enum AlbumSortKey {
   albumName,
   newestPhoto,
-  oldestPhoto,
   lastUpdated,
 }