Resolve deprecation warning for Rails.application.secrets

[lfilmeyer]

Seeing this warning when running specs:

DEPRECATION WARNING: `Rails.application.secrets` is deprecated in favor of `Rails.application.credentials` and will be removed in Rails 7.2. (called from <top (required)> at /Users/laura/dev/repos/urban-league-heat-pump-accelerator/backend/config/environment.rb:7)

[mzagaja]

I don't see this issue in the current version, is this still something you see @lfilmeyer ?