fix 'encode_plus' docstring for 'special_tokens_mask' (0s and 1s were reversed) (#7949)

* fix docstring for 'special_tokens_mask'

* revert auto formatter changes

* revert another auto format

* revert another auto format

src/transformers/tokenization_utils_base.py

@@ -1191,7 +1191,7 @@ ENCODE_PLUS_ADDITIONAL_KWARGS_DOCSTRING = r"""
               :obj:`return_overflowing_tokens=True`).
             - **num_truncated_tokens** -- Number of tokens truncated (when a :obj:`max_length` is specified and
               :obj:`return_overflowing_tokens=True`).
-            - **special_tokens_mask** -- List of 0s and 1s, with 0 specifying added special tokens and 1 specifying
+            - **special_tokens_mask** -- List of 0s and 1s, with 1 specifying added special tokens and 0 specifying
               regular sequence tokens (when :obj:`add_special_tokens=True` and :obj:`return_special_tokens_mask=True`).
             - **length** -- The length of the inputs (when :obj:`return_length=True`)
 """