Stop generating the [TOC] in the GN reference docs.

As doing so causes Gitiles to crash.

Also, update the docs with the response file change to
'gn refs'.

R=brettw@chromium.org
BUG=468851, https://code.google.com/p/gitiles/issues/detail?id=75

Review URL: https://codereview.chromium.org/1097423002

Cr-Original-Commit-Position: refs/heads/master@{#326176}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 36a275daed9a044694646530ab58694b487bad4e