Update broken_crypto.py to AES instead of Blowfish

Author: fatenhealy

python/ql/src/Security/CWE-327/examples/broken_crypto.py

@@ -6,7 +6,7 @@ def send_encrypted(channel, message):
     channel.send(cipher.encrypt(message)) # BAD: weak encryption
 
 
-cipher = Blowfish.new(SECRET_KEY)
+cipher = AES.new(SECRET_KEY)
 
 def send_encrypted(channel, message):
     channel.send(cipher.encrypt(message)) # GOOD: strong encryption