[EOSIO/eos] How to upgrade the system (eos) of BP nodes? (#5365)

The standard upgrade procedure is to read the [release notes](https://github.com/EOSIO/eos/releases) for each release and modify `config.ini` files accordingly. The `Removal Notices` sections are the most necessary sections to review when upgrading `nodeos`, as newly unrecognized options will prevent `nodeos` from starting, but the full notes should be reviewed for relevant changes.