chore: drop dead `userRentedActorIds` plumbing

[MQ37]

Problem

userRentedActorIds is dead code in this repo after #737. No tool reads it, but it is still parsed off _meta, threaded through InternalToolArgs, and forwarded to three tool.call(...) sites:

// src/mcp/server.ts
const userRentedActorIds = meta?.userRentedActorIds;          // line 766
// ...
await tool.call({ /* ... */ userRentedActorIds });            // lines 932, 968, 1342

Also declared on InternalToolArgs (src/types.ts:144) and on the _meta shape (src/types.ts:677).

Fix

Drop userRentedActorIds from InternalToolArgs, the _meta shape, the extraction in mcp/server.ts, the executeToolAndUpdateTask signature, and the three tool.call(...) sites.

Out of scope

apify-mcp-server-internal#500 covers dropping the upstream Mongo lookup that populates _meta.userRentedActorIds; this issue is the receiver-side cleanup in this repo.