Remove intro from gsn guide (#1886)
Remove intro from gsn guide (#1886)

* Remove intro from gsn guide

We are moving the intro to the top-level in the docsite, and focusing this guide into writing gsn-enabled contracts.

* Update docs/modules/ROOT/pages/gsn.adoc

Co-Authored-By: Francisco Giordano <4223852eec80914c4c190cdc031e06592b151a67@gmail.com>

* Update gsn.adoc

OpenZeppelin/zeppelin-solidity,OpenZeppelin/zeppelin-solidity,OpenZeppelin/openzeppelin-contracts,OpenZeppelin/openzeppelin-contracts,OpenZeppelin/zep-solidity,OpenZeppelin/zep-solidity,OpenZeppelin/openzeppelin-contracts