Fix WebAudio#2145: Update link to Audio EQ Cookbook (WebAudio#2146)

* Fix WebAudio#2145: Update link to Audio EQ Cookbook

Link to the fork that we maintain instead of the out-dated one at
w3.org.  Since we maintain this version, it's more likely to be
up-to-date with the information we want.

* Use correct link

index.bs

@@ -6039,7 +6039,7 @@ having very different characteristics. The formulas in this section
 describe the filters that a <a>conforming implementation</a> MUST
 implement, as they determine the characteristics of the different
 filter types. They are inspired by formulas found in the
-<a href="https://www.w3.org/2011/audio/audio-eq-cookbook.html">Audio EQ Cookbook</a>.
+<a href="https://webaudio.github.io/Audio-EQ-Cookbook/audio-eq-cookbook.html">Audio EQ Cookbook</a>.
 
 The {{BiquadFilterNode}} processes audio with a transfer function of