Fix link to GSN overview (#2053)

* Fix link to GSN overview

* Update contracts/GSN/README.adoc

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>

contracts/GSN/README.adoc

@@ -4,7 +4,7 @@ _Available since v2.4.0._
 
 This set of contracts provide all the tools required to make a contract callable via the https://gsn.openzeppelin.com[Gas Station Network].
 
-TIP: If you're new to the GSN, head over to our xref:openzeppelin::gsn/what-is-the-gsn.adoc[overview of the system] and basic guide to xref:ROOT:gsn.adoc[creating a GSN-capable contract].
+TIP: If you're new to the GSN, head over to our xref:learn::sending-gasless-transactions.adoc[overview of the system] and basic guide to xref:ROOT:gsn.adoc[creating a GSN-capable contract].
 
 The core contract a recipient must inherit from is {GSNRecipient}: it includes all necessary interfaces, as well as some helper methods to make interacting with the GSN easier.