Docs on `svelte/action` uses example of legacy mode

[mchoo7]

Describe the bug

The use: directive docs says

Legacy mode
Prior to the $effect rune, actions could return an object with update and destroy methods, where update would be called with the latest value of the argument if it changed. Using effects is preferred.

However there is no mention of the usage of $effect rune in svelte/action docs.

Reproduction

N/A

Logs

N/A

System Info

N/A

Severity

annoyance

[dummdidumm]

Actions in somewhat of a weird spot right now since they may at some point be deprecated in favor of attachments - the weird thing is, we might add $effect there (like, "use this instead of the update/destroy hooks" which nudges people to update their actions only to have to do that again when attachments land). For that reason I think it's ok that $effect is not mentioned there.