Fix: Correct ImportError for Metrics in test_parallel_report_download

The import path for the Metrics class in
examples/reporting/tests/test_parallel_report_download.py
was incorrect. It pointed to
google.ads.googleads.v19.resources.types.metrics,
but the Metrics class is defined in
google.ads.googleads.v19.common.types.metrics.

This commit updates the import path to the correct location,
resolving the ModuleNotFoundError that occurred when running the tests.

Author: google-labs-jules[bot]

examples/reporting/tests/test_parallel_report_download.py

@@ -19,7 +19,7 @@
 # from google.ads.googleads.v19.common.types import Value # Not used in current example but good to have if needed
 from google.ads.googleads.v19.resources.types.ad_group import AdGroup
 from google.ads.googleads.v19.resources.types.campaign import Campaign
-from google.ads.googleads.v19.resources.types.metrics import Metrics
+from google.ads.googleads.v19.common.types.metrics import Metrics
 from google.ads.googleads.v19.resources.types.google_ads_row import GoogleAdsRow
 
 class TestParallelReportDownload(unittest.TestCase):