Web speech API - minor fixes

[hamishwillee]

Minor fixes to add deprecation inline warnings on a deprecated API and remove experimental tagging in MDN that does not match BCD.

[github-actions]

Preview URLs

• https://pr10706.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/Web_Speech_API
• https://pr10706.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/Window/speechSynthesis

Flaws

None! 🎉

External URLs

URL: /en-US/docs/Web/API/Window/speechSynthesis
Title: Window.speechSynthesis
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/API/Web_Speech_API
Title: Web Speech API
on GitHub

No new external URLs