Update nand_gate.py

Author: koki0702

ch02/nand_gate.py

@@ -15,4 +15,4 @@ def NAND(x1, x2):
 if __name__ == '__main__':
     for xs in [(0, 0), (1, 0), (0, 1), (1, 1)]:
         y = NAND(xs[0], xs[1])
-        print(str(xs) + " -> " + str(y)) # 0を出力
+        print(str(xs) + " -> " + str(y))