Use auto-links for canvas (#9655)

Fix reference to outdated spec at the same time

Author: dontcallmedom

web-animations-2/Overview.bs

@@ -2203,8 +2203,7 @@ otherwise un-animatable attributes and properties, but potentially
 anything that is accessible via script, including even producing audio
 or creating vibrations.
 
-For example, using a <a>custom effect</a> that draws to a <a
-href="https://www.w3.org/TR/2dcontext/"><code>canvas</code></a>
+For example, using a <a>custom effect</a> that draws to a <{canvas}>
 element, it is possible to produce a complex animated effect
 featuring patterns that may be difficult to create using CSS or
 SVG.