Fixed system test version in owlbot.py

Author: gkevinzheng

owlbot.py

@@ -95,7 +95,7 @@ def place_before(path, text, *before_text, escape=None):
         "google-cloud-testutils",
         "opentelemetry-sdk"
     ],
-    system_test_python_versions=["3.19"],
+    system_test_python_versions=["3.9"],
     unit_test_python_versions=["3.7", "3.8", "3.9", "3.10", "3.11", "3.12", "3.13", "3.14"],
     unit_test_external_dependencies=["flask", "webob", "django"],
     samples=True,