refactor: Use canonical /v2/actors/ path instead of legacy /v2/acts/ alias (#833)

Switches the actor resource client URLs from the legacy `/v2/acts/...`
alias to the canonical `/v2/actors/...` family.

Follow-up to
[apify/apify-docs#2522](https://github.com/apify/apify-docs/pull/2522)
(and
[apify/apify-core#27780](https://github.com/apify/apify-core/pull/27780)),
which made `/v2/actors/...` the documented canonical path while keeping
`/v2/acts/...` as an undocumented alias. Non-breaking — the server still
accepts the legacy alias, but the client should hit the canonical path.