Remove `create_empty_secret` from `Makefile`

[michplunkett]

Description of Changes

With the addition of @sea-kelp's work on the email class, we should no longer need this cover up function for testing.

Tests and linting

• [x] This branch is up-to-date with the develop branch.
• [x] pytest passes on my local development environment.
• [x] pre-commit passes on my local development environment.

[michplunkett]

It looks like there isn't any conditional logic for binding files yet. One day.