Ensure application settings in tests adhere to FIPS requirements

What does this MR do and why?

When running tests in FIPS mode, ApplicationSetting by default has invalid SSH key size restrictions. We now ensure the FactoryBot creates a ApplicationSetting that conforms to FIPS requirements.

This can be tested via:

FIPS_MODE=true bundle exec rspec spec/services/application_settings/update_service_spec.rb spec/models/application_setting_spec.rb

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