Update the help text of bisect-builds.py tool.

This change is to update the help text to indicate that the tool supports reversed good/bad revision range.

BUG=none
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/11772002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@175384 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed