fix(jobs): switch to backoff.expo, shorter timeout (#5504)
fix(jobs): switch to backoff.expo, shorter timeout (#5504)

fixes #5490

My usage of retry_delay was wrong. It only retries 2 times.
I think using `backoff.expo` is just fine and we can reduce the
`max_time` too.

GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples