docs(firefox-release): Finalize release notes for Fx150 release

[dipikabh]

Description

This PR updates pages for Firefox 150 (release date: April 21, 2026).
Ran: node scripts/content/release-firefox.js 149
Output:

✅ Removed active status from Firefox 149
✅ Updated Firefox 150 to (Stable)
✅ Updated Firefox 151 to (Beta)
✅ Created new Nightly page for Firefox 152

[github-actions]

Preview URLs (4 pages)

• /en-US/docs/Mozilla/Firefox/Releases/149
• /en-US/docs/Mozilla/Firefox/Releases/150
• /en-US/docs/Mozilla/Firefox/Releases/151
• /en-US/docs/Mozilla/Firefox/Releases/152

Flaws (1)

Note! 3 documents with no flaws that don't need to be listed. 🎉

Found an unexpected or unresolvable flaw? Please report it here.

URL: /en-US/docs/Mozilla/Firefox/Releases/149
Title: Firefox 149 release notes for developers
Flaw count: 1

• macros:
  • Macro domxref produces link /en-US/docs/Web/API/structuredClone which is a redirect

External URLs (5)

URL: /en-US/docs/Mozilla/Firefox/Releases/150
Title: Firefox 150 release notes for developers (Stable)

• https://whattrainisitnow.com/release/?version=150 (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Mozilla/Firefox/Releases/151
Title: Firefox 151 release notes for developers (Beta)

• https://whattrainisitnow.com/release/?version=151 (1 time) (Note! This may be a new URL 👀)
• https://www.firefox.com/en-US/channel/desktop/ (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Mozilla/Firefox/Releases/152
Title: Firefox 152 release notes for developers (Nightly)

• https://whattrainisitnow.com/release/?version=152 (1 time) (Note! This may be a new URL 👀)
• https://www.firefox.com/en-US/channel/desktop/ (1 time) (Note! This may be a new URL 👀)

[pepelsbey]

Looks good! Thank you 🙂