Update comments for net/data/verify_certificate_chain_unittest/

net/data/verify_certificate_chain_unittest/intermediate-signed-with-md5/generate-chains.py

 #!/usr/bin/python
 # Copyright (c) 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-"""Certificate chain with 1 intermediate and a trusted root. The intermediate
-however is signed using the MD5 hash. Verification is expected to fail because
-MD5 is too weak."""
+"""Certificate chain where the intermediate has a valid signature, however uses
+MD5 in the signature algorithm."""
 
 import sys
 sys.path += ['..']
 
 import common
 
-# Self-signed root certificate (used as trust anchor).
+# Self-signed root certificate.
 root = common.create_self_signed_root_certificate('Root')
 
 # Intermediate.
 intermediate = common.create_intermediate_certificate('Intermediate', root)
 intermediate.set_signature_hash('md5')
 
 # Target certificate.
 target = common.create_end_entity_certificate('Target', intermediate)
 
 chain = [target, intermediate, root]
 common.write_chain(__doc__, chain, 'chain.pem')