fix(client): delete stale exported-any-returns entry for packages.update (#12207)

`22c42c9b` (#12062) bound `packages.update`'s return type, closing its
any-return under #11925, but `packages/client/exported-any-returns.json`
still carried the entry. The ledger is shrink-only and judged EXACTLY, so
the lingering entry reds `pnpm --filter @objectstack/client run
check:exported-any-returns` for every PR whose gate family includes the
client consumer gates.

Deletes exactly the `ObjectStackClient.packages.update` entry; every other
entry (still-open #11925/#12104 debt) is untouched, as is `$comment`.

Fixes #12193


Claude-Session: https://claude.ai/code/session_01KWRU3s15AJz7PGW7a7wdCh

Co-authored-by: Claude <noreply@anthropic.com>

Author: os-support-ai