removing imports and adding comment

pyrelacs/repros/calbi.py

@@ -1,5 +1,3 @@
-import signal
-import sys
 import faulthandler
 import time
 
@@ -8,13 +6,14 @@ import uldaq
 from IPython import embed
 import numpy as np
 import matplotlib.pyplot as plt
-from scipy.signal import welch, csd
+from scipy.signal import welch
 from scipy.signal import find_peaks
 
 from pyrelacs.devices.mccdac import MccDac
 from pyrelacs.util.logging import config_logging
 
 log = config_logging()
+# for more information on seg faults
 faulthandler.enable()