docs: correct regression-2453 comment accuracy

[RibatTRW]

Corrects two comment inaccuracies in tests/regression-2453.mjs from PR #2468:

1. Dependency note: uses node:fs, node:url and node:path only (node:child_process is NOT imported).
2. RED baseline note: T1 retired file present, T1 original file absent, T3 no other plugin claims RNBH.org and T4 content checks on a missing file all FAIL; T2x2 pass (exclusions already in the tsconfigs). After the fix: all six checks pass.

Comment text sourced from spec attachment; corrected attachment is authoritative. No code changes; comment lines only (5 insertions, 4 deletions).

This branch is stacked on #2468 (head 5984d12). The diff against master includes #2468's content until #2468 merges; the diff vs the #2468 head is comment-only, and the PR becomes comment-only against master once #2468 lands.

Checks run clean: node tests/regression-2453.mjs -> ALL CHECKS PASS; prettier --check clean.

[RibatTRW]

Merge order note: merge this PR (#2469) AFTER #2468.

This branch is stacked on #2468's head (5984d12). Once #2468 lands, this PR's diff becomes comment-only against master, as described in the PR body.

Merging this one first would force an add/add conflict on tests/regression-2453.mjs onto #2468. Both orders executed green during review; this order is the low-friction one.