fix(tests): fresh_env() now resets new environment values

Author: RobertCraigie

Diff for: tests/test_module_client.py

@@ -110,6 +110,7 @@ def fresh_env() -> Iterator[None]:
         _os.environ.clear()
         yield
     finally:
+        _os.environ.clear()
         _os.environ.update(old)