cleanup: Remove unused imports.

Generated by autoflake.

Signed-off-by: Anders Kaseorg <anders@zulipchat.com>

tools/test-bots

@@ -1,14 +1,12 @@
 #!/usr/bin/env python3
 
 from os.path import dirname, basename
-from importlib import import_module
 
 import os
 import sys
 import argparse
 import glob
 import unittest
-from unittest import TestCase, TestSuite
 import pytest
 
 def parse_args():