Trim yt-dlp pin comment, drop misleading WHATS_NEW page link

Self-review nits on PR #384:

- requirements.txt: 5-line comment for one pin → 1 line. Rationale
  lives in commit body and #367; no need to repeat in-tree.
- helper.js: dropped `page: 'settings'` from the yt-dlp WHATS_NEW
  entry. Settings page has no yt-dlp UI; the link would have
  navigated users somewhere irrelevant.

553 tests pass.

requirements.txt

@@ -27,12 +27,7 @@ beautifulsoup4>=4.12.0
 # System monitoring
 psutil>=6.0.0
 
-# YouTube support
-# Pinned to an exact version for reproducible builds. The Docker
-# entrypoint used to `pip install -U yt-dlp` on every container start,
-# which made startup non-deterministic and depended on PyPI being
-# reachable. Bump this pin in a SoulSync release when yt-dlp ships a
-# YouTube-fix update — that's the supported upgrade path now.
+# YouTube support — pinned for reproducible builds; bump per release. See #367.
 yt-dlp==2026.3.17
 
 # Lyrics support

webui/static/helper.js

@@ -3444,7 +3444,7 @@ const WHATS_NEW = {
     '2.4.1': [
         // --- post-2.4.0 dev work — entries hidden by _getLatestWhatsNewVersion until the build version bumps ---
         { date: 'Unreleased — 2.4.1 dev cycle' },
-        { title: 'Faster Docker Startup — yt-dlp Pinned', desc: 'docker startup used to run `pip install -U yt-dlp` on every container start. removed that — yt-dlp is now pinned in requirements.txt so startup is fast and reproducible. tradeoff: youtube fixes ship via soulsync releases now instead of next container restart.', page: 'settings' },
+        { title: 'Faster Docker Startup — yt-dlp Pinned', desc: 'docker startup used to run `pip install -U yt-dlp` on every container start. removed that — yt-dlp is now pinned in requirements.txt so startup is fast and reproducible. tradeoff: youtube fixes ship via soulsync releases now instead of next container restart.' },
     ],
     '2.4.0': [
         // --- April 26, 2026 — Search & Artists unification + reorganize queue ---