Update SANSDarkRunBackgroundCorrection docs

Refs #20820

docs/source/algorithms/SANSDarkRunBackgroundCorrection-v1.rst

@@ -48,8 +48,8 @@ Usage
     in_y = ws_sample.dataY(0)
     out_y = out_ws.dataY(0)
 
-    print "The first bin of the first spectrum of the input was " + str(in_y[0])
-    print "After the dark run correction it is " + str(out_y[0])
+    print("The first bin of the first spectrum of the input was " + str(in_y[0]))
+    print("After the dark run correction it is " + str(out_y[0]))
 
 Output: