wg-actuator: Fix docker image build

[BrianJKoopman]

Description

This PR fixes the docker image build for the simonsobs/ocs-wgactuator-agent image.

Motivation and Context

Resolves #1015.

How Has This Been Tested?

Image built locally. Not yet run against the hardware.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.