Move boundary loading rake task to migrator repo (2 SP)

[ryanrolds]

Is your feature request related to a problem? Please describe.
Each night we are checking if any boundaries need to be added. This is unnecessary as we only add boundaries about once a month.

Describe the solution you'd like
Move the boundary files and the Rake task for loading them from the main repo to the migrator repo. This ticket should result in two PRs one that adds the Rake task, the s3 downloads in buildspec.yaml, and a PR that removes those items from the main repo.

Additional context
Once this is done we will set up a special CodeBuild project that will just run the boundary update. This will allow us to run it on demand through the AWS Console. This will reduce the time it takes to deploy the frontend, which has been getting slower because the Docker image takes longer to build with the larger files.