[build] Docker failing to load images in dev build

[imnasnainaec]

Describe the bug

When running deploy/scripts/build.py, the builds are not automatically loaded in Docker as before.

To Reproduce

Steps to reproduce the behavior:

0. Delete all local Docker images, containers, builds for The Combine
1. Start a Python virtual environment (venv)
2. Run python deploy/scripts/setup_cluster.py --type development
3. Run python deploy/scripts/build.py
4. Run docker images and see that the desired images aren't present
5. Run kubectl -n thecombine get deployments and see 0/1 in the READY column (should be 1/1)
6. Run kubectl -n thecombine get pods to get failed pod names (e.g. backend-9d66df89b-m25pq)
7. Run (e.g.) kubectl -n thecombine logs backend-9d66df89b-m25pq to see that the image failed to pull
8. Run python deploy/scripts/build.py --debug and you may notice warning like

WARNING: No output specified with docker-container driver. Build result will only remain in the build cache. To push result image into registry use --push or to load image into docker use --load

It seems some Docker or buildx update no longer loads our builds by default and we need to add --load to the docker buildx build [...] commands.