chore: get retry after value in a pythonic way

it uses the python framework to solve the problem related to retry after returns a string like "50, 49" in retry response header when the status code is 429

issue related: airbytehq#13673

airbyte-integrations/connectors/source-zendesk-support/source_zendesk_support/streams.py

@@ -88,7 +88,7 @@ def backoff_time(self, response: requests.Response) -> Union[int, float]:
         The response has a Retry-After header that tells you for how many seconds to wait before retrying.
         """
 
-        retry_after = int(to_int(response.headers.get("Retry-After", 0)))
+        retry_after = int(response.headers.get("Retry-After", "0").split(",")[0])
         if retry_after > 0:
             return retry_after