Fix change log generation in push-to-trunk script.

Fixed missing parenthesis in regular expression. The log checker matched on the word "true" and included a wrong change log entry.

TEST=python -m unittest test_scripts.ToplevelTest.testRegressWrongLogEntryOnTrue
R=ulan@chromium.org

Review URL: https://codereview.chromium.org/99573003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@18220 ce2b1a6d-e550-0410-aec6-3dcde31c8c00