Minor comment rewrites.

python/lsst/validate/drp/calcsrd/adx.py

@@ -97,15 +97,17 @@ def measureADx(metric, amx, afx_spec):
         # We subtract AFx from 100.  So AFx = 10 becomes threshold = 90.
         threshold = 100 - afx_spec.threshold.value
 
-        # In AstroPy 3, numpy.percentitle of an array with quantities
+        # In AstroPy 3,
+        #   numpy.percentitle of an array with quantities
         #   (incorrectly) returns a unitless number
-        # In AstroPy 4, numpy.percentitle of an array with Quantities
-        #   correct returns a number with the same units as the input array.
+        # In AstroPy 4 + numpy >= 1.17,
+        #   numpy.percentitle of an array with Quantities
+        #   correctly returns a number with the same units as the input array.
         # To be compatible with both Astropy 3.2 and Astropy 4, we:
         # 1. Extract the array in marcsec and convert to a value.
         # 2. Calculate the numpy.percentitle of this unitless array
         # 3. Multiply that result by u.marcsec to get the right units.
-        rmsDistMas = amx.extras['rmsDistMas'].quantity.to(u.marcsec).value,
+        rmsDistMas = amx.extras['rmsDistMas'].quantity.to(u.marcsec).value
         afxAtPercentile = np.percentile(rmsDistMas, threshold)
         afxAtPercentile *= u.marcsec
         quantity = afxAtPercentile - amx.quantity