[DOCS] Fix hard-coded accessibility link (elastic#209611)

(cherry picked from commit caf12e5)

Author: lcawl

docs/developer/best-practices/index.asciidoc

@@ -20,7 +20,7 @@ Are you planning with scalability in mind?
 
 Did you know {kib} makes a public statement about our commitment to
 creating an accessible product for people with disabilities?
-https://www.elastic.co/guide/en/kibana/master/accessibility.html[We do]!
+<<accessibility,We do>>!
 It’s very important all of our apps are accessible.
 
 * Learn how https://elastic.github.io/eui/#/guidelines/accessibility[EUI