Update `coreth` links to `avalanchego`

[navillanueva]

Not sure if this is the correct place to send this message, but wanted to pass this along to you all!
https://platwizards.slack.com/archives/C0758P2745C/p1764001247453239?thread_ts=1763989976.133229&cid=C0758P2745C
We have been working to get rid of the coreth repository entirely, and tomorrow plan to archive the repository, as it gets integrate with the AvalancheGo repository. There are a number of references / links to coreth in the docs -- I am not sure what the correct course of action is, but as of tomorrow the links to the git repository at least will be out of date, and I wanted to let you all know!

(https://avalancheavax.slack.com/archives/G01CW5QK80M/p1764012968222739?thread_ts=1764012938.229509&cid=G01CW5QK80M)
for this page: https://build.avax.network/academy/avalanche-l1/customizing-evm/02-intro-to-evm/05-different-evm-versions#precompile-evm
at least, while not immediately, the eventual goal is that libevm will be the only fork of geth we use