MAINT: use explicit value of n_jobs to avoid hangs on Windows (scikit-learn#13970)

Author: oleksandr-pavlyk

sklearn/model_selection/tests/test_search.py

@@ -1757,7 +1757,7 @@ def test_empty_cv_iterator_error():
 
  train_size = 100
  ridge = RandomizedSearchCV(Ridge(), {'alpha': [1e-3, 1e-2, 1e-1]},
- cv=cv, n_jobs=-1)
+ cv=cv, n_jobs=4)
 
  # assert that this raises an error
  with pytest.raises(ValueError,
@@ -1779,7 +1779,7 @@ def get_n_splits(self, *args, **kw):
 
  train_size = 100
  ridge = RandomizedSearchCV(Ridge(), {'alpha': [1e-3, 1e-2, 1e-1]},
- cv=cv, n_jobs=-1)
+ cv=cv, n_jobs=4)
 
  # assert that this raises an error
  with pytest.raises(ValueError,