Manually delete fixture in `test_mysqli_flush_sync()`.

This test creates a dummy post and subsequently runs a query containing
`DROP PROCEDURE`. This latter query implies a `COMMIT`, which means that the
post is not cleaned up for later tests. Manually deleting the post with
`wp_delete_post()` solves this problem.

Fixes #28155.
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git-svn-id: http://core.svn.wordpress.org/trunk@30319 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Twenty Fifteen: reduce the margins on the editor body in esitor-style.css. Fixes #30331.
Built from https://develop.svn.wordpress.org/trunk@30321


git-svn-id: http://core.svn.wordpress.org/trunk@30320 1a063a9b-81f0-0310-95a4-ce76da25c4cd