Removed blurb about change in .index internals.

Jim (Fulton) points out that it's not entirely clear that
the new format can't be read by older ZODBs, and Tim doesn't
think it's worth the bother to find out for sure.

NEWS.txt

@@ -49,12 +49,6 @@ BTrees
 FileStorage
 -----------
 
-- The main part of a ``Data.fs.index`` index file now uses an OOBTree
-  instead of a Python dictionary.  A consequence is that ``.index`` files
-  written by this version of ZODB cannot be read by earlier versions of
-  ZODB.  Older ``.index`` files can be read by this version of ZODB, and
-  are automatically converted to use the new scheme.
-
 - Addded a record iteration protocol to FileStorage.  You can use the
   record iterator to iterate over all current revisions of data
   pickles in the storage.