Flaky test: `test_kernel_request_priority_over_idle_tasks`

Here's a concrete example from a recent version bump, from "Test macOS / Rust: stable, R: 4.2, OS: macos-14":https://github.com/posit-dev/ark/actions/runs/23856689091/job/69551676589#logs ``` stderr ─── thread 'test_kernel_request_priority_over_idle_tasks' (38550) panicked at crates/ark/tests/data_explorer_priority.rs:101:5: get_schema took 358.499375ms, which suggests kernel requests are being starved by idle tasks ``` Also seen here: https://github.com/posit-dev/ark/actions/runs/23855419750/job/69546947120 And here: https://github.com/posit-dev/ark/actions/runs/23821845591/job/69435773862