[docs] Broken link in Python 2.7.2 Tutorial

[Remco Janssen]

Dear Madam, Sir,

It seems the 'next' links on top and bottom of the '1. Whetting Your Appetite' 
page in the Python Tutorial (http://docs.python.org/tutorial/appetite.html) 
are broken.

Probably this was introduced during modifications made on June 25th, because I 
didn't encounter this problem before those modifications.

Best regards,
Remco Janssen