Tests: remove unused Python modules from freshclam tests

The 'cgi' module is deprecrated and will be removed in Python 3.13.
We weren't using it anyways.

Fixes: https://github.com/Cisco-Talos/clamav/issues/1327

unit_tests/freshclam_test.py

@@ -10,14 +10,10 @@ import os
 from pathlib import Path
 import platform
 import shutil
-import subprocess
-import sys
-import time
 import unittest
 from functools import partial
 
 from http.server import HTTPServer, BaseHTTPRequestHandler
-import cgi
 
 import testcase