Improve explore projects spinach test

Project name "Internal" is too generic and can lead to false
positive/negative when there is a visibility filter on the page. So we
ensure we check for project inside list holder css class.
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

features/steps/shared/project.rb

@@ -166,12 +166,16 @@ module SharedProject
   end
 
   step 'I should see project "Internal"' do
+    page.within '.js-projects-list-holder' do
       expect(page).to have_content "Internal"
     end
+  end
 
   step 'I should not see project "Internal"' do
+    page.within '.js-projects-list-holder' do
       expect(page).not_to have_content "Internal"
     end
+  end
 
   step 'public project "Community"' do
     create(:project, :public, :repository, name: 'Community')