fix: force joblib for test_gui_run_simulations

Author: gtdang

hnn_core/tests/test_gui.py

@@ -395,7 +395,7 @@ def test_gui_run_simulations(setup_gui):
     tstop_trials_tstep = [(10, 1, 0.25),
                           (10, 2, 0.5),
                           (12, 1, 0.5)]
-    assert gui.widget_backend_selection.value == "Joblib"
+    gui.widget_backend_selection.value = "Joblib"
     sim_count = 0
 
     for val_tstop, val_ntrials, val_tstep in tstop_trials_tstep: