Fixup

demos/critical_filtering.py

 import nifty5 as ift
-from nifty5.library.nonlinearities import Linear, Tanh, Exponential
 import numpy as np
+from nifty5 import Exponential, Linear, Tanh
+
 np.random.seed(42)
 
 

demos/nonlinear_critical_filter.py

 import nifty5 as ift
-from nifty5.library.nonlinearities import Exponential
+from nifty5 import Exponential
 import numpy as np
 np.random.seed(42)