docs: add comment for max_workers

docs/examples/simulator/plot_run_mass_point_model.py

@@ -124,6 +124,7 @@ serial_time = time.time() - start
 serial_output = run_mpm_simulator.outputs
 
 start = time.time()
+# max_workers controls maximum number of tasks running in parallel
 run_mpm_simulator.parallel_run(var_samples, prefixes=parallel_prefixes, max_workers=4)
 parallel_time = time.time() - start
 parallel_output = run_mpm_simulator.outputs