Fix albumtypes plugin and its tests

The new database type DelimitedString does list to string and vice versa
conversions itself.

beetsplug/albumtypes.py

@@ -55,7 +55,7 @@ class AlbumTypesPlugin(BeetsPlugin):
             bracket_r = ''
 
         res = ''
-        albumtypes = item.albumtypes.split('; ')
+        albumtypes = item.albumtypes
         is_va = item.mb_albumartistid == VARIOUS_ARTISTS_ID
         for type in types:
             if type[0] in albumtypes and type[1]:

test/test_albumtypes.py

@@ -106,6 +106,6 @@ class AlbumTypesPluginTest(unittest.TestCase, TestHelper):
 
     def _create_album(self, album_types: [str], artist_id: str = 0):
         return self.add_album(
-            albumtypes='; '.join(album_types),
+            albumtypes=album_types,
             mb_albumartistid=artist_id
         )