html: update quotes about the list of active formatting elements

See https://html.spec.whatwg.org/multipage/parsing.html#the-list-of-active-formatting-elements

Updates golang/go#23071

Change-Id: I015c394ed34d721e9e4a4d3e797d06d750c1864e
Reviewed-on: https://go-review.googlesource.com/94837
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

html/node.go

@@ -21,10 +21,10 @@ const (
 	scopeMarkerNode
 )
 
-// TODO(namusyaka): These elements should be updated.
-// Section 12.2.4.3 says "The markers are inserted when entering applet
-// elements, buttons, object elements, marquees, table cells, and table
-// captions, and are used to prevent formatting from 'leaking'".
+// Section 12.2.4.3 says "The markers are inserted when entering applet,
+// object, marquee, template, td, th, and caption elements, and are used
+// to prevent formatting from "leaking" into applet, object, marquee,
+// template, td, th, and caption elements".
 var scopeMarker = Node{Type: scopeMarkerNode}
 
 // A Node consists of a NodeType and some Data (tag name for element nodes,