Update existing tests for file-by-file nav

spec/features/merge_request/user_views_auto_expanding_diff_spec.rb

@@ -27,9 +27,10 @@ RSpec.describe 'User views diffs file-by-file', :js do
     page.within('#diffs') do
       expect(page).not_to have_content('This diff is collapsed')
 
-      click_button 'Next'
+      find('.page-link.next-page-item').click
 
       expect(page).not_to have_content('This diff is collapsed')
+      expect(page).to have_selector('.diff-file .file-title', text: 'large_diff_renamed.md')
     end
   end
 end

spec/features/merge_request/user_views_diffs_file_by_file_spec.rb

@@ -25,7 +25,7 @@ RSpec.describe 'User views diffs file-by-file', :js do
       expect(page).to have_selector('.file-holder', count: 1)
       expect(page).to have_selector('.diff-file .file-title', text: '.DS_Store')
 
-      click_button 'Next'
+      find('.page-link.next-page-item').click
 
       expect(page).to have_selector('.file-holder', count: 1)
       expect(page).to have_selector('.diff-file .file-title', text: '.gitignore')