Modify regex

[AInitikesh]

ollama:deepseek-coder-v2
Generates code like bellow

 ```python
def add(a, b):
    if b == 0:
        return float('inf')  # Using infinity to avoid division by zero
    else:
        return a / b
add(1,0)

where there is space before ```python causing the output to be incorrect. Need to modify the lang_indicator as follows.

lang_indicator = r"^\s*```[a-zA-Z0-9]\s\n"

[srdas]

@AInitikesh Thanks for noticing this and raising the issue, as well as the proposed fix in magics.py. Why not open a PR with the correction, showing the problem first and the fix after the code change? Also test to make sure it does not break python code generation by other LLMs? Add screenshots as needed. You can use the Contributor documentation to set up for this: https://jupyter-ai.readthedocs.io/en/latest/contributors/index.html.