fix program 25 to behave as described in comment

Currently 25.prg produces different output than is described in the comment ```# print 14, 12, 10, ... 0```. As written, it produces the following output: ``` 0 12 10 8 6 4 2 ``` The following PR, modifies 25.prg to produce the output as described in the program comment. ``` 14 12 10 8 6 4 2 0 ```