readme: fix broken link (ethereum#26612)

Author: delihiros

README.md

@@ -363,7 +363,7 @@ Please make sure your contributions adhere to our coding guidelines:
  * Commit messages should be prefixed with the package(s) they modify.
    * E.g. "eth, rpc: make trace configs optional"
 
-Please see the [Developers' Guide](https://geth.ethereum.org/docs/developers/devguide)
+Please see the [Developers' Guide](https://geth.ethereum.org/docs/developers/geth-developer/dev-guide)
 for more details on configuring your environment, managing project dependencies, and
 testing procedures.