Fix a markup error (multiple <dfn>s)

The following commit introduced a markup error that prevented building:
whatwg@a4b9eef

source

@@ -59977,8 +59977,8 @@ enum <dfn>CanvasDirection</dfn> { "<span data-x="dom-context-2d-direction-ltr">l
 interface <dfn>CanvasPathDrawingStyles</dfn> {
   // line caps/joins
   attribute unrestricted double <span data-x="dom-context-2d-lineWidth">lineWidth</span>; // (default 1)
-  attribute <dfn>CanvasLineCap</dfn> <span data-x="dom-context-2d-lineCap">lineCap</span>; // (default "butt")
-  attribute <dfn>CanvasLineJoin</dfn> <span data-x="dom-context-2d-lineJoin">lineJoin</span>; // (default "miter")
+  attribute <span>CanvasLineCap</span> <span data-x="dom-context-2d-lineCap">lineCap</span>; // (default "butt")
+  attribute <span>CanvasLineJoin</span> <span data-x="dom-context-2d-lineJoin">lineJoin</span>; // (default "miter")
   attribute unrestricted double <span data-x="dom-context-2d-miterLimit">miterLimit</span>; // (default 10)
 
   // dashed lines
@@ -59991,9 +59991,9 @@ interface <dfn>CanvasPathDrawingStyles</dfn> {
 interface <dfn>CanvasTextDrawingStyles</dfn> {
   // text
   attribute DOMString <span data-x="dom-context-2d-font">font</span>; // (default 10px sans-serif)
-  attribute <dfn>CanvasTextAlign</dfn> <span data-x="dom-context-2d-textAlign">textAlign</span>; // (default: "start")
-  attribute <dfn>CanvasTextBaseline</dfn> <span data-x="dom-context-2d-textBaseline">textBaseline</span>; // (default: "alphabetic")
-  attribute <dfn>CanvasDirection</dfn> <span data-x="dom-context-2d-direction">direction</span>; // (default: "inherit")
+  attribute <span>CanvasTextAlign</span> <span data-x="dom-context-2d-textAlign">textAlign</span>; // (default: "start")
+  attribute <span>CanvasTextBaseline</span> <span data-x="dom-context-2d-textBaseline">textBaseline</span>; // (default: "alphabetic")
+  attribute <span>CanvasDirection</span> <span data-x="dom-context-2d-direction">direction</span>; // (default: "inherit")
 };
 
 [NoInterfaceObject, Exposed=(Window,Worker)]