Fix "SyntaxWarning: invalid escape sequence" for regex compile function in Python 3.12

[vietjovi]

There are language changes in Python 3.12 that prevents the regex pattern from retrieving IP addresses and protocol strings from proxy data. The fix was tested with versions 3.10, 3.11, and 3.12.

A backslash-character pair that is not a valid escape sequence now generates a SyntaxWarning, instead of DeprecationWarning. For example, re.compile("\d+.\d+") now emits a SyntaxWarning ("\d" is an invalid escape sequence, use raw strings for regular expression: re.compile(r"\d+.\d+")). In a future Python version, SyntaxError will eventually be raised, instead of SyntaxWarning. (Contributed by Victor Stinner in python/cpython#98401.)

Reference: https://docs.python.org/3/whatsnew/3.12.html#other-language-changes