[css-shapes-2] Use <<position>> for shape() staring point (#11649)

Closes #11358

Author: noamr

css-shapes-2/Overview.bs

@@ -155,7 +155,7 @@ The ''shape()'' Function</h4>
 	e.g., when computing the rendered 'clip-path'.
 
 	<pre class=prod>
-		<dfn>shape()</dfn> = shape( <<'fill-rule'>>? from <<coordinate-pair>>, <<shape-command>>#)
+		<dfn>shape()</dfn> = shape( <<'fill-rule'>>? from <<position>>, <<shape-command>>#)
 	</pre>
 
 	The <<'fill-rule'>> is interpreted identically to the same argument in ''path()''.
@@ -166,8 +166,7 @@ The ''shape()'' Function</h4>
 
 	The <css>from <<coordinate-pair>></css> represents the starting point for the first shape-command.
 	It adds an initial <a href="https://www.w3.org/TR/SVG/paths.html#PathDataMovetoCommands">absolute moveto</a>
-	to the list of path data commands,
-	with the <<coordinate-pair>> measured from the top-left corner of the [=reference box=].
+	to the list of path data commands.
 
 	The sequence of <dfn><<shape-command>></dfn>s represent
 	further <a href="https://www.w3.org/TR/SVG11/paths.html#PathData">path data commands</a>.