That was then, this is now.
Rename 'ZODB.FileStorage.FileStorage' as 'ZODB.filestorage._impl'.

The expected API to get to the 'FileStorage' class is now::

  import ZODB.filestorage # and use FileStorage attr

or::

  from ZODB.filestorage import FileStorage

BBB aliases exist to support code which imported the 'FileStorage' class
via 'ZODB.FileStorage'  or 'ZODB.FileStorage.FileStorage'.