Fix typo in python dependency install instructions

[josfam]

• Add requirements.txt file to the pip install command

[esteecodes]

considering the requirements.txt currently contains only openai would it not be sufficient to go with

pip install openai

and maybe adding -r requirements.txt only if there are multiple dependencies added in the future
just a thought good catch either way

[josfam]

@monacodelisa , good point with that pip install -r requirements.txt maybe being overkill for now because of the single dependency on openai.
Didn't think about it like that.