Fix docstring for language code in mBart
diff --git a/src/transformers/models/mbart/tokenization_mbart.py b/src/transformers/models/mbart/tokenization_mbart.py
index d96e69fe30130..e8425fe8c539e 100644
--- a/src/transformers/models/mbart/tokenization_mbart.py
+++ b/src/transformers/models/mbart/tokenization_mbart.py
@@ -153,7 +153,7 @@ def build_inputs_with_special_tokens(
         adding special tokens. An MBART sequence has the following format, where ``X`` represents the sequence:
 
         - ``input_ids`` (for encoder) ``X [eos, src_lang_code]``
-        - ``decoder_input_ids``: (for decoder) ``[tgt_lang_code] X [eos]``
+        - ``decoder_input_ids``: (for decoder) ``X [eos, tgt_lang_code]``
 
         BOS is never used. Pairs of sequences are not the expected use case, but they will be handled without a
         separator.
@@ -220,13 +220,13 @@ def prepare_seq2seq_batch(
         return model_inputs
 
     def set_src_lang_special_tokens(self, src_lang) -> None:
-        """Reset the special tokens to the source lang setting. No prefix and suffix=[eos, cur_lang_code]."""
+        """Reset the special tokens to the source lang setting. No prefix and suffix=[eos, src_lang_code]."""
         self.cur_lang_code = self.lang_code_to_id[src_lang]
         self.prefix_tokens = []
         self.suffix_tokens = [self.eos_token_id, self.cur_lang_code]
 
     def set_tgt_lang_special_tokens(self, lang: str) -> None:
-        """Reset the special tokens to the target language setting. Prefix [tgt_lang_code], suffix =[eos]."""
+        """Reset the special tokens to the target language setting. No prefix and suffix=[eos, tgt_lang_code]."""
         self.cur_lang_code = self.lang_code_to_id[lang]
         self.prefix_tokens = []
         self.suffix_tokens = [self.eos_token_id, self.cur_lang_code]
diff --git a/src/transformers/models/mbart/tokenization_mbart_fast.py b/src/transformers/models/mbart/tokenization_mbart_fast.py
index c25b291c2a05c..56e7c065f3914 100644
--- a/src/transformers/models/mbart/tokenization_mbart_fast.py
+++ b/src/transformers/models/mbart/tokenization_mbart_fast.py
@@ -152,7 +152,7 @@ def build_inputs_with_special_tokens(
         An MBART sequence has the following format, where ``X`` represents the sequence:
 
         - ``input_ids`` (for encoder) ``X [eos, src_lang_code]``
-        - ``decoder_input_ids``: (for decoder) ``[tgt_lang_code] X [eos]``
+        - ``decoder_input_ids``: (for decoder) ``X [eos, tgt_lang_code]``
 
         BOS is never used. Pairs of sequences are not the expected use case, but they will be handled without a
         separator.
@@ -218,7 +218,7 @@ def prepare_seq2seq_batch(
         return model_inputs
 
     def set_src_lang_special_tokens(self, src_lang) -> None:
-        """Reset the special tokens to the source lang setting. No prefix and suffix=[eos, cur_lang_code]."""
+        """Reset the special tokens to the source lang setting. No prefix and suffix=[eos, src_lang_code]."""
         self.cur_lang_code = self.convert_tokens_to_ids(src_lang)
         self.prefix_tokens = []
         self.suffix_tokens = [self.eos_token_id, self.cur_lang_code]
@@ -233,7 +233,7 @@ def set_src_lang_special_tokens(self, src_lang) -> None:
         )
 
     def set_tgt_lang_special_tokens(self, lang: str) -> None:
-        """Reset the special tokens to the target language setting. Prefix [tgt_lang_code], suffix =[eos]."""
+        """Reset the special tokens to the target language setting. No prefix and suffix=[eos, tgt_lang_code]."""
         self.cur_lang_code = self.convert_tokens_to_ids(lang)
         self.prefix_tokens = []
         self.suffix_tokens = [self.eos_token_id, self.cur_lang_code]

# What does this PR do?

Fixes #8534


## Before submitting
- [X] This PR fixes a typo or improves the docs.


## Who can review?

@patrickvonplaten 
