Fix CONTRIBUTING.md file (#4328)

Replaces "go-ethereum" with "Erigon"

.github/CONTRIBUTING.md

@@ -4,7 +4,7 @@ Thank you for considering to help out with the source code! We welcome
 contributions from anyone on the internet, and are grateful for even the 
 smallest of fixes!
 
-If you'd like to contribute to go-ethereum, please fork, fix, commit and send a 
+If you'd like to contribute to Erigon, please fork, fix, commit and send a 
 pull request for the maintainers to review and merge into the main code base. If
 you wish to submit more complex changes though, please check up with the core 
 devs first on [Discord server](https://github.com/ledgerwatch/erigon#erigon-discord-server) to