Update example_startup_script.sh (#1240)
Update example_startup_script.sh (#1240)

On latest Debian 9 image on GCP this startup script fails with this error:

Nov 30 17:03:33 localhost startup-script: INFO startup-script: E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples