Use class methods for VersionCheck

All of these methods are stateless, there was no point to have them as
instance methods.

Mostly this allows us to remove an `allow_any_instance_of` usage.

app/helpers/version_check_helper.rb

@@ -6,8 +6,7 @@ module VersionCheckHelper
     return unless Gitlab::CurrentSettings.version_check_enabled
     return if User.single_user&.requires_usage_stats_consent?
 
-    image_url = VersionCheck.new.url
-    image_tag image_url, class: 'js-version-status-badge'
+    image_tag VersionCheck.url, class: 'js-version-status-badge'
   end
 
   def link_to_version

lib/version_check.rb

@@ -5,16 +5,17 @@ require "base64"
 # This class is used to build image URL to
 # check if it is a new version for update
 class VersionCheck
-  def data
+  def self.data
     { version: Gitlab::VERSION }
   end
 
-  def url
+  def self.url
     encoded_data = Base64.urlsafe_encode64(data.to_json)
+
     "#{host}?gitlab_info=#{encoded_data}"
   end
 
-  def host
+  def self.host
     'https://version.gitlab.com/check.svg'
   end
 end

spec/features/help_pages_spec.rb

@@ -54,9 +54,10 @@ describe 'Help Pages' do
 
   context 'in a production environment with version check enabled', :js do
     before do
-      allow(Rails.env).to receive(:production?) { true }
       stub_application_setting(version_check_enabled: true)
-      allow_any_instance_of(VersionCheck).to receive(:url) { '/version-check-url' }
+
+      allow(Rails.env).to receive(:production?).and_return(true)
+      allow(VersionCheck).to receive(:url).and_return('/version-check-url')
 
       sign_in(create(:user))
       visit help_path

spec/helpers/version_check_helper_spec.rb

@@ -13,21 +13,21 @@ describe VersionCheckHelper do
       before do
         allow(Rails.env).to receive(:production?) { true }
         allow(Gitlab::CurrentSettings.current_application_settings).to receive(:version_check_enabled) { true }
-        allow_any_instance_of(VersionCheck).to receive(:url) { 'https://version.host.com/check.svg?gitlab_info=xxx' }
-
-        @image_tag = helper.version_status_badge
+        allow(VersionCheck).to receive(:url) { 'https://version.host.com/check.svg?gitlab_info=xxx' }
       end
 
       it 'should return an image tag' do
-        expect(@image_tag).to match(/^<img/)
+        expect(helper.version_status_badge).to start_with('<img')
       end
 
       it 'should have a js prefixed css class' do
-        expect(@image_tag).to match(/class="js-version-status-badge lazy"/)
+        expect(helper.version_status_badge)
+          .to match(/class="js-version-status-badge lazy"/)
       end
 
       it 'should have a VersionCheck url as the src' do
-        expect(@image_tag).to match(%r{src="https://version\.host\.com/check\.svg\?gitlab_info=xxx"})
+        expect(helper.version_status_badge)
+          .to include(%{src="https://version.host.com/check.svg?gitlab_info=xxx"})
       end
     end
   end