TinyMCE: Use the correct syntax for allowing an `embed` element to be a valid...

TinyMCE: Use the correct syntax for allowing an `embed` element to be a valid child of an `object` element.

Fixes a bug in TinyMCE when using its HTML5 schema definition.

props azaozz.
see #22790.
for trunk.
... with the right patch this time. [23142] was done in error.



git-svn-id: https://core.svn.wordpress.org/trunk@23144 1a063a9b-81f0-0310-95a4-ce76da25c4cd