Move helper function

`test_utils.py` is actually a file for testing some utils, not
some utils for testing.

Test helper functions and fixtures are better placed in conftest,
and also means that we can use them in conftest.

tests/app/main/views/test_dashboard.py

@@ -21,8 +21,8 @@ from tests.conftest import (
     SERVICE_ONE_ID,
     mock_get_inbound_sms_summary,
     mock_get_inbound_sms_summary_with_no_messages,
+    normalize_spaces,
 )
-from tests.app.test_utils import normalize_spaces
 
 stub_template_stats = [
     {