Remove unnecessary tests and expectations related with loading-bar

These expectations are already covered by attach_new_file, so they are no longer needed:
>  expect(page).to have_css ".loading-bar.complete"

We can remove the tests:
> "Should update loading bar style after invalid file upload"
because the expectation:
> expect(page).to have_css ".loading-bar.errors"
It is already tested in "Should not update document cached_attachment field after invalid file upload"

spec/system/nested_documentable_spec.rb

@@ -111,24 +111,6 @@ describe "Nested documentable" do
         expect(page).to have_field("Title", with: "My Title")
       end
 
-      scenario "Should update loading bar style after valid file upload" do
-        do_login_for(user, management: management_section?(path))
-        visit path
-
-        documentable_attach_new_file(file_fixture("empty.pdf"))
-
-        expect(page).to have_css ".loading-bar.complete"
-      end
-
-      scenario "Should update loading bar style after invalid file upload" do
-        do_login_for(user, management: management_section?(path))
-        visit path
-
-        documentable_attach_new_file(file_fixture("logo_header.gif"), success: false)
-
-        expect(page).to have_css ".loading-bar.errors"
-      end
-
       scenario "Should update document cached_attachment field after valid file upload" do
         do_login_for(user, management: management_section?(path))
         visit path