Remove parent divs only once for each ul element

[mateusdeap]

Fixes #2039

The issue was that, in Docs::Cpref::CleanHtmlFilter, we had the following:

        css('div > ul').each do |node|
          node.parent.before(node.parent.children).remove
        end

This was fine for almost all cases, however, the page for std::vector::vector had more than one ul element inside the same div (in the Complexity section).

This meant that, as we iterated over each ul element, because 2 or more had the same parent div, for the first ul with a sibling, we'd correctly pop all it's siblings out of the parent div, but when we came around to the second sibling ul, it's parent div was now some outer div on the page, and that would get removed. This would repeat itself how many sibling ul elements there might be on the page.

I modified the code to simply grab the parent divs, remove the duplicates and then execute the logic to pop out it's children and remove itself.

All tests passed locally, but when I went ahead to add tests to prevent this bug from reappearing, I noticed that there doesn't seem to be any tests for specific scrapers or filters, is that by choice?

[thewheat]

This also sees to fix #1610

[jasonbtiller]

This looks great. Why hasn't it been merged?

[mateusdeap]

I do not know hahaha I just assumed that, eventually, the maintainer would se it. Do you know who I need to ping, maybe?

[simon04]

Thank you!