Update comments for net/data/verify_certificate_chain_unittest/

net/data/verify_certificate_chain_unittest/target-signed-by-512bit-rsa/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 target
-certificate is signed using a weak RSA key (512-bit modulus), and so
-verification is expected to fail."""
+"""Certificate chain where the target certificate is signed using a weak RSA
+key (512-bit modulus)."""
 
 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 with a very weak key size (512-bit RSA).
 intermediate = common.create_intermediate_certificate('Intermediate', root)
 intermediate.set_key(common.get_or_generate_rsa_key(
     512, common.create_key_path(intermediate.name)))
 
 # Target certificate.
 target = common.create_end_entity_certificate('Target', intermediate)
 
 chain = [target, intermediate, root]
 common.write_chain(__doc__, chain, 'chain.pem')