[css-shapes-2] Fix fill-rule reference

Author: heycam

css-shapes-2/Overview.bs

@@ -25,6 +25,8 @@ spec:css-shapes-1;
 	type:function; text: path()
 spec:css-writing-modes-4; type:concept; text:physical
 spec:css-writing-modes-4; type:concept; text:"writing mode"
+spec:svg2; type:property;
+	text:fill-rule
 </pre>
 
 <style type="text/css">
@@ -140,10 +142,10 @@ The ''shape()'' Function</h4>
 	such as additional units and math functions.
 
 	<pre class=prod>
-		<dfn>shape()</dfn> = shape( <<fill-rule>>? from <<coordinate-pair>>, <<shape-command>>#)
+		<dfn>shape()</dfn> = shape( <<'fill-rule'>>? from <<coordinate-pair>>, <<shape-command>>#)
 	</pre>
 
-	The <<fill-rule>> is interpreted identically to the same argument in ''path()''.
+	The <<'fill-rule'>> is interpreted identically to the same argument in ''path()''.
 
 	The rest of the arguments define a list of path data commands,
 	identical to that of an <a href="https://www.w3.org/TR/SVG11/paths.html#PathData">SVG Path</a>,