Remove unused lets from deploy_key spec

spec/models/deploy_key_spec.rb

 require 'spec_helper'
 
 describe DeployKey, models: true do
-  let(:project) { create(:project) }
-  let(:deploy_key) { create(:deploy_key, projects: [project]) }
-
   describe "Associations" do
     it { is_expected.to have_many(:deploy_keys_projects) }
     it { is_expected.to have_many(:projects) }