[a] (0) Fix the conditions for </p> omission
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=26981
Affected topics: HTML, HTML Syntax and Parsing

git-svn-id: https://svn.whatwg.org/webapps@8841 340c8d12-0b0e-0410-8428-c7bf67bfef74