Remove broken special case for ancient worlds

And to whoever wrote that thing: "World10" is not 6 characters
long, so the workaround was broken anyway.

overviewer_core/world.py

@@ -780,12 +780,7 @@ def get_worlds():
             if not os.path.exists(world_dat): continue
             info = nbt.load(world_dat)[1]
             info['Data']['path'] = os.path.join(save_dir, dir).decode(loc)
-            if dir.startswith("World") and len(dir) == 6:
-                try:
-                    world_n = int(dir[-1])
-                    ret[world_n] = info['Data']
-                except ValueError:
-                    pass
+
             if 'LevelName' in info['Data'].keys():
                 ret[info['Data']['LevelName']] = info['Data']