exB: stop setting the number of threads

exercises/exerciseB/numerical_integration_solution.py

@@ -19,7 +19,7 @@ def main(arg):
                 errors = pool.map(compute_error, ns)
         case 'mt':
             from multiprocessing.pool import ThreadPool
-            with ThreadPool(10) as pool:
+            with ThreadPool() as pool:
                 errors = pool.map(compute_error, ns)
 
     for n, e in zip(ns, errors):