Use main instead of master

[blinkdog]

lta was created during the olden days of master being the default branch.

To get consistent with current code practices, we should change over to using main as the default branch.

Note: There is a dependency in Kubernetes, which is using the image with the master tag.
These two issues should be addressed at the same time to prevent deployment issues.

[ric-evans]

Note: There is a dependency in Kubernetes, which is using the image with the master tag.
These two issues should be addressed at the same time to prevent deployment issues.

Adding details from in-person conversation:
If/when we adopt a semantic versioning (tag) release pattern, we will be able to make the changeover to main easily. IRL, with this, our default branch could be foo if we wanted.