delete extra CDN header (#2315)

Author: guru-desh

docs/glossary.md

@@ -24,12 +24,6 @@ Learn More at [Wikipedia](https://en.wikipedia.org/wiki/Application_binary_inter
 
 ## CDN
 
-Content Delivery Network. CDNs are geographically distributed networks of servers that mirror the contents of a primary source. Having multiple servers offering the same content increases performance (reduced latency, higher download speeds) and availability.
-
-[Learn more](https://en.wikipedia.org/wiki/Content_delivery_network).
-
-## CDN
-
 **C**ontent **D**elivery **N**etwork. CDNs are geographically distributed networks of servers that mirror
 contents of a primary source. Having multiple servers offering the same content increases
 performance (reduced latency, higher download speeds) and availability.