Test sometimes takes longer than a second.

Tests are supposed to take less than 1 second to pass. This test usually runs under 1 second, however it occasionally runs a little longer than 1 second. Doesn't appear often but does appear from time to time. Might be worth investigating?

`FAILED tests/unit_tests/hyperion/experiment_plans/test_grid_detect_then_xray_centre_plan.py::test_when_full_grid_scan_run_then_parameters_sent_to_fgs_as_expected - Failed: Timeout >1.0s`