TinyMCE: fix error trying to translate non-existent button "title" in the...

TinyMCE: fix error trying to translate non-existent button "title" in the compat3x plugin. See #24067.
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git-svn-id: https://core.svn.wordpress.org/trunk@26871 1a063a9b-81f0-0310-95a4-ce76da25c4cd