fix llama2 chat system prompt
# What does this PR do?

Fixes the Llama 2 System Prompt so its consistent with METAs version.

When testing my finetuning script, I found that the official LLAMA Code and the Huggingface code returned different tokens for the same code, apparently due to different linebreaks.

Code to test:

```python
#from https://github.com/facebookresearch/llama/blob/6c7fe276574e78057f917549435a2554000a876d/llama/generation.py#L46C11-L46C11
DEFAULT_SYSTEM_PROMPT = """\
You are a helpful, respectful and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature.

If a question does not make any sense, or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information."""

tokenizer = LlamaTokenizer.from_pretrained("/Users/jph/dev2/models/Llama-2-7b-chat-hf")
token_llama=tokenizer.encode(DEFAULT_SYSTEM_PROMPT)
from transformers.models.llama.tokenization_llama import DEFAULT_SYSTEM_PROMPT as DEFAULT_SYSTEM_PROMPT_TRANSFORMERS
token_hf=tokenizer.encode(DEFAULT_SYSTEM_PROMPT_TRANSFORMERS_FAST)
for i in range(100):
    print (f"llama: {tokenizer.decode(token_llama[i])} , transformers: {tokenizer.decode(token_hf[i])}")
    if token_llama[i]!=token_hf[i]:
        print('!!!')
```
which returns:
```
...
llama: being , transformers: being
llama: safe , transformers: safe
llama: . , transformers: .
llama: Your , transformers: Your
llama: answers , transformers: ans
!!!
llama: should , transformers: wers
...
```

I don't know how big the difference is, but it surely doesn't make sense to deviate here (even if there is no performance issue and it's just for debugging reasons).

## Who can review?

@ArthurZucker @sgugger 

> Hey! Thanks for catching this. There seems to be a missing space in our prompt, here: `Youranswers should not include...`.
> 
> I can't accept the PR in the current state as the formating is there to comply with our linters. If you can just add the missing space would be great! Thanks for catching this. We have a test in the conversational pipeline, which did not detect this!

sure; tried to fix the formatting and make it more readable....<|||||>Hey! Sorry, #24930 is ready, we'll merge it in favor of this one! Thanks a lot for pointing out and contributing! 🤗 <|||||>> Hey! Sorry, #24930 is ready, we'll merge it in favor of this one! Thanks a lot for pointing out and contributing! 🤗

sure, didnt see that there was another PR fixing this. 
But just for next time - why did the checks still fail? I have absolutely no idea from the CircleCI messages how to check myself or what the reason is, lines should be short enough?<|||||>You have to run the linter! The lines are probably too short this time and can be optimised haha! Use `make style` again after each changed. 