Quick spelling clean-up in the auto-bisect code.

Note: I prefer "try server" and "try bot" more than "tryserver" and "trybot" because that's what's used in the official documentation: http://dev.chromium.org/developers/testing/try-server-usage

BUG=

Review URL: https://codereview.chromium.org/468633005

Cr-Commit-Position: refs/heads/master@{#291579}
6 files changed