Move admin logs spinach test to rspec

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

changelogs/unreleased/move-admin-logs-spinach-test-to-rspec.yml

+---
+title: Move admin logs spinach test to rspec
+merge_request: 7945
+author: Semyon Pupkov

features/admin/logs.feature

-@admin
-Feature: Admin Logs
-  Background:
-    Given I sign in as an admin
-
-  Scenario: On Admin Logs
-    Given I visit admin logs page
-    Then I should see tabs with available logs

features/steps/admin/logs.rb → spec/features/admin/admin_browses_logs_spec.rb

-class Spinach::Features::AdminLogs < Spinach::FeatureSteps
-  include SharedAuthentication
-  include SharedPaths
-  include SharedAdmin
+require 'spec_helper'
+
+describe 'Admin browses logs' do
+  before do
+    login_as :admin
+  end
+
+  it 'shows available log files' do
+    visit admin_logs_path
 
-  step 'I should see tabs with available logs' do
     expect(page).to have_content 'test.log'
     expect(page).to have_content 'githost.log'
     expect(page).to have_content 'application.log'