CI flake: `test_confirmed_reads`: `Pending` vs `Poll::ready()`

[bfops]

https://github.com/clockworklabs/SpacetimeDB/actions/runs/26790115775/job/78974819711

thread 'subscription::module_subscription_actor::tests::test_confirmed_reads' (82992) panicked at crates/core/src/subscription/module_subscription_actor.rs:2769:9:
assertion failed: `(left matches right)`

Diff < left / right > :
<Pending
>Poll::Ready(_)


note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace