Fixing list type when using max_features param in plot()

[DenizY7]

When calling plot() with the max_features parameter, it crashes with the following error:

TypeError                                 Traceback (most recent call last)
script.py()
----> 1 sage.plot(sage_values, feature_names=list(X_test.columns), max_features=20)

File c:\<redacted>\Anaconda3\envs\lumc\lib\site-packages\sage\plotting.py:85, in plot(explanation, feature_names, sort_features, max_features, orientation, error_bars, confidence_level, capsize, color, title, title_size, tick_size, tick_rotation, label_size, figsize, return_fig)
     83 else:
     84     assert 0 < confidence_level < 1
---> 85     std = std * norm.ppf(0.5 + confidence_level / 2)
     87 # Make plot.
     88 fig = plt.figure(figsize=figsize)

TypeError: can't multiply sequence by non-int of type 'numpy.float64'

This change casts the std variable as np.array when max_features is set, to fix this issue.