readme: use correct link for web3.js docs (ethereum#24046)

Previous link leads to incorrect (more recent) version of web3.js docs.

go-ethereum uses v0.20.1. The docs for 0.2x.x have been archived at this Github link.

README.md

@@ -68,7 +68,7 @@ This command will:
    causing it to download more data in exchange for avoiding processing the entire history
    of the Ethereum network, which is very CPU intensive.
  * Start up `geth`'s built-in interactive [JavaScript console](https://geth.ethereum.org/docs/interface/javascript-console),
-   (via the trailing `console` subcommand) through which you can interact using [`web3` methods](https://web3js.readthedocs.io/) 
+   (via the trailing `console` subcommand) through which you can interact using [`web3` methods](https://github.com/ChainSafe/web3.js/blob/0.20.7/DOCUMENTATION.md) 
    (note: the `web3` version bundled within `geth` is very old, and not up to date with official docs),
    as well as `geth`'s own [management APIs](https://geth.ethereum.org/docs/rpc/server).
    This tool is optional and if you leave it out you can always attach to an already running