More regex as string literal

[jmartin-tech]

Python 3.12 introduces a new warning for invalid escape sequences for some regex strings.

Update string literal notation for regex.

Found during testing:

% python -m garak -m huggingface.Model -n meta-llama/Llama-2-7b-chat-hf -p dan.AutoDAN
...
🕵️  queue of probes: dan.AutoDAN
garak/garak/resources/autodan/genetic.py:234: SyntaxWarning: invalid escape sequence '\s'
  sentences1 = [s for s in re.split("(?<=[.!?])\s+", str1) if s]
/garak/garak/resources/autodan/genetic.py:235: SyntaxWarning: invalid escape sequence '\s'
  sentences2 = [s for s in re.split("(?<=[.!?])\s+", str2) if s]
[nltk_data] Downloading package stopwords to

[erickgalinkin]

LGTM