Remove hashlib from python/app.py

[danbarr]

We should pull hashlib out of the demo app.py file since it triggers the known edge case with archived package detection (stacklok/codegate#518).

@lukehinds I suspect you originally included this to demonstrate CodeGate picking up on usage of a weak hashing algorithm (MD5) during its security review? Any alternate ideas, and maybe there's an actually deprecated package we could include?