Add note to chromium cq config to get sign-off from chrome-eng-review per wiki.
Add note to chromium cq config to get sign-off from chrome-eng-review per wiki.

We couldn't put this note in the config file when it was json because there was no support for comments.

Review URL: https://codereview.chromium.org/1274183004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#346387}

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