Update tokenizer_config.json

Add the "generation" tags in the chat template to be able to use the `return_assistant_mask=True` option in `Tokenizer.apply_chat_template` (see PR https://github.com/huggingface/transformers/pull/30650).

Example:
```py
import transformers
tokenizer = transformers.AutoTokenizer.from_pretrained("mistralai/Codestral-22B-v0.1")
tokenized = tokenizer.apply_chat_template(
[
{"role": "user", "content": """Hello assistant"""},
{"role": "assistant", "content": "Hello user"},
{"role": "user", "content": "How are you?"},
{"role": "assistant", "content": "I'm good"},
],
return_assistant_tokens_mask=True,
return_dict=True,
)
print(tokenized)

# BEFORE:
# {'input_ids': [1, 3, 23325, 14660, 4, 23325, 2956, 2, 3, 2370, 1228, 1136, 29572, 4, 1083, 29510, 29487, 1947, 2], 'attention_mask': [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1], 'assistant_masks': [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]}
# AFTER:
# {'input_ids': [1, 3, 23325, 14660, 4, 23325, 2956, 2, 3, 2370, 1228, 1136, 29572, 4, 1083, 29510, 29487, 1947, 2], 'attention_mask': [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1], 'assistant_masks': [0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1]}
```

tokenizer_config.json

@@ -6173,7 +6173,7 @@
     }
   },
   "bos_token": "<s>",
-  "chat_template": "{%- if messages[0]['role'] == 'system' %}\n    {%- set system_message = messages[0]['content'] %}\n    {%- set loop_messages = messages[1:] %}\n{%- else %}\n    {%- set loop_messages = messages %}\n{%- endif %}\n\n{{- bos_token }}\n{%- for message in loop_messages %}\n    {%- if (message['role'] == 'user') != (loop.index0 % 2 == 0) %}\n        {{- raise_exception('After the optional system message, conversation roles must alternate user/assistant/user/assistant/...') }}\n    {%- endif %}\n    {%- if message['role'] == 'user' %}\n        {%- if loop.last and system_message is defined %}\n            {{- '[INST] ' + system_message + '\\n\\n' + message['content'] + '[/INST]' }}\n        {%- else %}\n            {{- '[INST] ' + message['content'] + '[/INST]' }}\n        {%- endif %}\n    {%- elif message['role'] == 'assistant' %}\n        {{- ' ' + message['content'] + eos_token}}\n    {%- else %}\n        {{- raise_exception('Only user and assistant roles are supported, with the exception of an initial optional system message!') }}\n    {%- endif %}\n{%- endfor %}\n",
+  "chat_template": "{%- if messages[0]['role'] == 'system' %}\n    {%- set system_message = messages[0]['content'] %}\n    {%- set loop_messages = messages[1:] %}\n{%- else %}\n    {%- set loop_messages = messages %}\n{%- endif %}\n\n{{- bos_token }}\n{%- for message in loop_messages %}\n    {%- if (message['role'] == 'user') != (loop.index0 % 2 == 0) %}\n        {{- raise_exception('After the optional system message, conversation roles must alternate user/assistant/user/assistant/...') }}\n    {%- endif %}\n    {%- if message['role'] == 'user' %}\n        {%- if loop.last and system_message is defined %}\n            {{- '[INST] ' + system_message + '\\n\\n' + message['content'] + '[/INST]' }}\n        {%- else %}\n            {{- '[INST] ' + message['content'] + '[/INST]' }}\n        {%- endif %}\n    {%- elif message['role'] == 'assistant' %}\n        {%- generation %}\n            {{- ' ' + message['content'] + eos_token}}\n        {%- endgeneration %}\n    {%- else %}\n        {{- raise_exception('Only user and assistant roles are supported, with the exception of an initial optional system message!') }}\n    {%- endif %}\n{%- endfor %}\n",
   "clean_up_tokenization_spaces": false,
   "eos_token": "</s>",
   "legacy": false,