DOC: fix docstring

Author: ColmTalbot

bilby/gw/detector/interferometer.py

@@ -589,7 +589,7 @@ def optimal_snr_squared(self, signal):
 
         Returns
         =======
-        float: The optimal signal to noise ratio possible squared
+        float: The optimal signal-to-noise ratio squared of the signal
         """
         return (abs(self.whiten_frequency_series(signal))**2).sum()