fix(functions): fix Python dependencies example

[Shillaker]

Summary

• Remove copy-pasted README content that did not work
• Update to use serverless-python-requirements

Checklist

• [x] I have reviewed this myself.
• [x] I have attached a README to my example. You can use this template as reference.
• [ ] I have updated the project README to link my example.

[cyclimse]

Sorry for the late review, but it looks great to me! :heart: Thanks a lot for using the python requirements integration ^^

I was able to deploy this from my personal machine yesterday, so I'm not sure what was the problem we got with serverless-python-requirements :thinking:

Cheers!