Twenty Fifteen: Remove a non-relevant part of a string in 404.php.

props davidakennedy.
fixes #30061.
Built from https://develop.svn.wordpress.org/trunk@29990


git-svn-id: http://core.svn.wordpress.org/trunk@29732 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: Include post title in Continue Reading link in Link post format.

props davidakennedy.
fixes #30070.
Built from https://develop.svn.wordpress.org/trunk@29991


git-svn-id: http://core.svn.wordpress.org/trunk@29733 1a063a9b-81f0-0310-95a4-ce76da25c4cd