Update README link to learn guide (#2070)

Reported from Community Member via Intercom

README.md

@@ -38,7 +38,7 @@ contract MyNFT is ERC721Full, ERC721Mintable {
 }
 ```
 
-_If you're new to smart contract development, head to [Developing Smart Contracts](https://docs.openzeppelin.com/contracts/learn::developing-smart-contracts) to learn about creating a new project and compiling your contracts._
+_If you're new to smart contract development, head to [Developing Smart Contracts](https://docs.openzeppelin.com/learn/developing-smart-contracts) to learn about creating a new project and compiling your contracts._
 
 To keep your system secure, you should **always** use the installed code as-is, and neither copy-paste it from online sources, nor modify it yourself.