fix: manually add cleverapi.bigbluebus.com intermediate certificate to image

[themightychris]

Description

Provides a short-term fix to https://github.com/cal-itp/data-infra/issues/3452.

Type of change

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

How has this been tested?

Running curl -vvvv https://cleverapi.bigbluebus.com/ within the locally-built container image

Post-merge follow-ups

• [ ] Deploy new image tag to cluster