Heartbeat: fix comment spelling

git-svn-id: https://core.svn.wordpress.org/trunk@24544 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE: normalize font size for H1 - H6 submenu, fixes #24586.

git-svn-id: https://core.svn.wordpress.org/trunk@24545 1a063a9b-81f0-0310-95a4-ce76da25c4cd