Update fql.md (#3623)

redirected old url `/docs/config-api/fql` to new one `/docs/app/config-api/fql`

Author: mschasz

src/api/config-api/fql.md

@@ -1,5 +1,7 @@
 ---
 title: Destination Filter Query Language
+redirect_from:
+  - '/docs/config-api/fql'
 ---
 
 {% include content/papi-ga.html %}