fix the most egregious issue with the use of python logging

[ekalosak]

From the Python 3.11 docs, emphasis added:
"""
debug(msg, *args, **kwargs)

Logs a message with level DEBUG on this logger. The msg is the message format string, and the args are the arguments which are merged into msg using the string formatting operator. (Note that this means that you can use keywords in the format string, together with a single dictionary argument.) No % formatting operation is performed on msg when no args are supplied.
"""

The simplest reproducible error case is: python -c 'import logging; logging.warning("asdf", "qwer");'
The expected result is a stack trace.

To fix: logger.warning("asdf %s", "qwer");

Please note that the firebase-functions-python codebase has a tremendous number of instances of this logging usage error. I'm only fixing the one that I encounter most frequently here, but it might be useful to perform a systematic review of the logging usage throughout the package.