Use consistent spelling for request.referer

- 'referer', although gramatically incorrect, is the
  spelling in the HTTP spec, as well as the actual
  (non-aliased) method name on the request object.

app/views/projects/services/_form.html.haml

@@ -8,7 +8,7 @@
 
 = form_for(integration, as: :service, url: scoped_integration_path(integration), method: :put, html: { class: 'gl-show-field-errors integration-settings-form js-integration-settings-form', data: { 'test-url' => test_project_service_path(@project, integration) } }) do |form|
   = render 'shared/service_settings', form: form, integration: integration
-  %input{ id: 'services_redirect_to', type: 'hidden', name: 'redirect_to', value: request.referrer }
+  %input{ id: 'services_redirect_to', type: 'hidden', name: 'redirect_to', value: request.referer }
 
 - if lookup_context.template_exists?('show', "projects/services/#{integration.to_param}", true)
   %hr

app/views/users/show.html.haml

@@ -23,7 +23,7 @@
             data: { toggle: 'tooltip', placement: 'bottom', container: 'body' } }>
             = sprite_icon('error')
         - else
-          = link_to new_abuse_report_path(user_id: @user.id, ref_url: request.referrer), class: link_classes + 'btn gl-button btn-default btn-icon',
+          = link_to new_abuse_report_path(user_id: @user.id, ref_url: request.referer), class: link_classes + 'btn gl-button btn-default btn-icon',
             title: s_('UserProfile|Report abuse'), data: { toggle: 'tooltip', placement: 'bottom', container: 'body' } do
             = sprite_icon('error')
       - if can?(current_user, :read_user_profile, @user)

spec/views/projects/services/_form.haml_spec.rb

@@ -16,7 +16,7 @@ RSpec.describe 'projects/services/_form' do
       can?: true,
       current_application_settings: Gitlab::CurrentSettings.current_application_settings,
       integration: project.redmine_service,
-      request: double(referrer: '/services')
+      request: double(referer: '/services')
     )
   end