fix: wait time instead of tries (#10378)

Author: engelke

appengine/standard_python3/bundled-services/deferred/django/main_test.py

@@ -68,7 +68,7 @@ def version():
     version_hostname = f"{version_id}-dot-{project_id}.appspot.com"
 
     # Wait for app to initialize
-    @backoff.on_exception(backoff.expo, requests.exceptions.HTTPError, max_tries=3)
+    @backoff.on_exception(backoff.expo, requests.exceptions.HTTPError, max_time=300)
     def wait_for_app(url):
         r = requests.get(url)
         r.raise_for_status()