fix: functions_to_trace typing

[rcmarron]

Problem

This updates the type of the functions_to_trace param to match the latest changes.

The expected format introduced here is:

functions_to_trace = [
    {"qualified_name": "tests.test_basics._hello_world_counter"},
    {"qualified_name": "time.sleep"},
    {"qualified_name": "collections.Counter.most_common"},
]

But the current type is List[str]

[rcmarron]

cc @antonpirker, I think this is your domain.

[sentrivana]

Thanks for spotting this and fixing it, @rcmarron! It's also wrong in the docs, I'll push a fix.