chore: update `Sudid` destructure docs

[peetzweg]

The docs destructure an array element form the Sudid event. This is no longer available. It is now a named field called sudo_result.

Came up in this substack question: https://substrate.stackexchange.com/questions/10981/property-iserror-does-not-exist-on-type-codec-when-showing-sudo-events

And here is the actual Event defintion: https://github.com/paritytech/polkadot-sdk/blob/e2caa813bfd2973e7a7a74aa5292433397dbc787/substrate/frame/sudo/src/lib.rs#L302-L306