EXAMPLE: fix seed settings

examples/gw_examples/injection_examples/fast_tutorial.py

@@ -9,7 +9,6 @@ between luminosity distances of 100Mpc and 5Gpc, the cosmology is Planck15.
 """
 
 import bilby
-import numpy as np
 
 # Set the duration and sampling frequency of the data segment that we're
 # going to inject the signal into