TinyMCE Classic Block: fix the Edit Image modal to work as in the Classic Editor.

Fixes #46085.

git-svn-id: https://develop.svn.wordpress.org/trunk@44695 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/css/editor.css

@@ -1211,6 +1211,10 @@ i.mce-i-wp_code:before {
 	content: "\f104";
 }
 
+.mce-content-body dl.wp-caption {
+	max-width: 100%;
+}
+
 /* Quicktags */
 .quicktags-toolbar {
 	padding: 3px;