Deprecate secrets.yml.example file in favor of secrets.yml

Problem

Once we communicate to the engineering group to move secret overrides from secrets.yml to .env and the duration to shift is complete, we can move to the next step:

• commit secrets.yml to the repository which will be a replica of secrets.yml.example
• remove secrets.yml.example from the repository

This is important because application code still uses Rails secrets (example), and will ensure development environments do not break when application code is updated to use Rails Credentials & env file.

Proposal

• rename secrets.yml.example to secrets.yml