[python3 migration] remove py-mock: import mock from unittest

use from unittest import mock instead of import mock

and remove py-mock libs from Android.bp

BUG: 137195528
Test: atest acloud_test --host
Change-Id: I349e7b5c184f2271402b73804d025db981f18dd5
diff --git a/setup/gcp_setup_runner_test.py b/setup/gcp_setup_runner_test.py
index 7e4dac4..e4a0e92 100644
--- a/setup/gcp_setup_runner_test.py
+++ b/setup/gcp_setup_runner_test.py
@@ -17,7 +17,8 @@
 
 import unittest
 import os
-import mock
+
+from unittest import mock
 import six
 
 # pylint: disable=no-name-in-module,import-error,no-member