doc: fix headings for CHANGELOG_v10.md

The LTS bit flip did not include the new title heading for LTS in the
changelog. This commit fixes that.

PR-URL: https://github.com/nodejs/node/pull/23973


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>