View the original community article here
Last tested: Jun 21, 2017
Per-Schedule
In Looker 4.20+, there is an option in the scheduler modal to "Include Links" for each scheduled report.
Instance-wide
There is also a Whitelabel section of the Admin page where you can turn this off globally.
Note: This requires the Whitelabel license feature to be turned on, contact your Looker account manager if you want to make use of this feature.
This content is subject to limited support.