Fix GCP GPG Key Error in Docker Build

[devstein]

Description

CI has been failing the past few nights with the following error

#6 2.295 W: GPG error: https://packages.cloud.google.com/apt cloud-sdk InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY B53DC80D13EDEF05
#6 2.296 E: The repository 'https://packages.cloud.google.com/apt cloud-sdk InRelease' is not signed.

I'm not sure what unpinned underlying dependency changed to cause this issue, but adding GCP keys per these instructions appears to fix it.

Checklist

• Wrote a description of my changes above
• Formatted my code with black
• Added a bullet point for my changes to the top of the CHANGELOG.md file
• Added or modified unit tests to reflect my changes
• Manually tested with a notebook
• If adding a feature, there is an example notebook and/or documentation in the README.md file