Enable the Buy CI Minutes button for Groups with free or trial plan

Changes that were initially added to hide this button has been reverted
given now it's possible to purchase extra CI minutes for free plans.

ee/app/models/ee/namespace.rb

@@ -292,12 +292,6 @@ module EE
       actual_plan_name == GOLD_PLAN
     end
 
-    def paid_plan?
-      return false if trial?
-
-      !(free_plan? || early_adopter_plan?)
-    end
-
     def use_elasticsearch?
       ::Gitlab::CurrentSettings.elasticsearch_indexes_namespace?(self)
     end

ee/app/services/fetch_subscription_plans_service.rb

 # frozen_string_literal: true
 
 class FetchSubscriptionPlansService
-  URL = 'https://customers.gitlab.com/gitlab_plans'.freeze
+  URL = "#{EE::SUBSCRIPTIONS_URL}/gitlab_plans".freeze
 
   def initialize(plan:)
     @plan = plan

ee/app/views/groups/pipeline_quota/index.html.haml

@@ -10,10 +10,9 @@
     %strong= @group.name
     group
 
-  - if @group.paid_plan?
-    .col-sm-6
-      %p.text-right
-        = link_to 'Buy additional minutes', 'https://customers.gitlab.com/subscriptions', target: '_blank', class: 'btn btn-inverted btn-success right text-right'
+  .col-sm-6
+    %p.text-right
+      = link_to 'Buy additional minutes', EE::SUBSCRIPTIONS_PLANS_URL, target: '_blank', class: 'btn btn-inverted btn-success right text-right'
 
 = render "namespaces/pipelines_quota/list",
   locals: { namespace: @group, projects: @projects }

ee/app/views/shared/_gold_trial_callout_content.html.haml

@@ -13,7 +13,7 @@
           %p.mb-0
             %span= _('Try all GitLab has to offer for 30 days.')
             %span.d-none.d-sm-inline= _('No credit card required.')
-        = link_to _('Start your trial'), 'https://customers.gitlab.com/trials/new?gl_com=true', class: "btn btn-primary mt-2 mt-sm-0 #{button_css_class}", target: '_blank'
+        = link_to _('Start your trial'), "#{EE::SUBSCRIPTIONS_URL}/trials/new?gl_com=true", class: "btn btn-primary mt-2 mt-sm-0 #{button_css_class}", target: '_blank'
 
       - if is_dismissable
         %button.btn.btn-default.close.js-close{ type: 'button',

ee/spec/models/ee/namespace_spec.rb

@@ -56,39 +56,4 @@ describe Namespace do
       expect(namespace.use_elasticsearch?).to eq(true)
     end
   end
-
-  describe '#paid_plan?' do
-    using RSpec::Parameterized::TableSyntax
-
-    let(:namespace) { create(:namespace) }
-
-    before(:all) do
-      %i[free_plan early_adopter_plan bronze_plan silver_plan gold_plan].each do |plan|
-        create(plan)
-      end
-    end
-
-    subject { namespace.paid_plan? }
-
-    where(:plan_code, :trial, :expected_result) do
-      described_class::FREE_PLAN          | false | false
-      described_class::EARLY_ADOPTER_PLAN | false | false
-      described_class::BRONZE_PLAN        | false | true
-      described_class::SILVER_PLAN        | false | true
-      described_class::GOLD_PLAN          | false | true
-      described_class::BRONZE_PLAN        | true  | false
-      described_class::SILVER_PLAN        | true  | false
-      described_class::GOLD_PLAN          | true  | false
-    end
-
-    with_them do
-      before do
-        namespace.update!(gitlab_subscription_attributes: { trial: trial, hosted_plan: Plan.find_by_name(plan_code) })
-      end
-
-      it do
-        is_expected.to eq(expected_result)
-      end
-    end
-  end
 end