fix(browser_tool): fall through to autodetect on config read failure

tests/tools/test_browser_cloud_provider_cache.py

@@ -10,7 +10,7 @@ All other ``None`` outcomes (no credentials yet, config read error, explicit
 provider instantiation failure) leave the cache unset so the next call retries.
 """
 import logging
-from unittest.mock import Mock, patch
+from unittest.mock import Mock
 
 import pytest