Tweak definition based on WCAG 2.x backlog meeting feedback

guidelines/terms/21/single-pointer.html

@@ -1,5 +1,5 @@
 <dt><dfn>single pointer</dfn></dt>
 <dd>
-   <p>an input – such as a mouse, stylus, or finger on a touch screen – that only targets a single point on the screen (as opposed to multi-pointer/multi-touch scenarios)</p>
+   <p>an input that only targets a single point on the page/screen at a time – such as a mouse, stylus, or single finger on a touch screen – as opposed to multi-pointer/multi-touch scenarios</p>
 </dd>