[e] (0) Update registerProtocolHandler() section to have the method names in the heading
Fixing https://www.w3.org/Bugs/Public/show_bug.cgi?id=26875
Affected topics: DOM APIs

git-svn-id: https://svn.whatwg.org/webapps@8820 340c8d12-0b0e-0410-8428-c7bf67bfef74