Make max_length consistent across defaults in generate function and max-length default.

generate_openelm.py

@@ -188,7 +188,7 @@ def openelm_generate_parser():
         '--max_length',
         dest='max_length',
         help='Maximum length of tokens.',
-        default=256,
+        default=1024,
         type=int,
     )
     parser.add_argument(