Remove spec files (#9751)

Nothing to test.

spec/models/account_warning_preset_spec.rb

-require 'rails_helper'
-
-RSpec.describe AccountWarningPreset, type: :model do
-  pending "add some examples to (or delete) #{__FILE__}"
-end

spec/models/account_warning_spec.rb

-require 'rails_helper'
-
-RSpec.describe AccountWarning, type: :model do
-  pending "add some examples to (or delete) #{__FILE__}"
-end