tools: do not autolink section to itself

Fix a regression in the new doc generation toolchain.

PR-URL: https://github.com/nodejs/node/pull/22138


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Sam Ruby <rubys@intertwingly.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>