Update no-spec msg for PushManager.*

[teoli2003]

This is part of #6108.

We are dealing with features that are no more on the standard track (deprecated), with bcd tables. The idea is to remove the {{Specifications}}, that implies missing data in this case, without putting back an outdated table like before

Dealing with the 4 PushManager methods: hasPermission, register, unregister, and registrations.

• I removed the {{Specifications}} macro and replaced it with a basic text.
• I updated the text at the top too.
• I delete PushRegistrationManager not implemented at all (and not on standard track)
• I updated the Push API page not to mention PushRegistrationManager anymore.

I removed some gremlins too.

[github-actions]

Preview URLs

• https://pr6223.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/PushManager
• https://pr6223.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/PushManager/unregister
• https://pr6223.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/PushManager/register
• https://pr6223.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/PushManager/hasPermission
• https://pr6223.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/PushManager/registrations
• https://pr6223.content.dev.mdn.mozit.cloud/en-US/docs/Web/API/Push_API

Flaws

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

URL: /en-US/docs/Web/API/PushManager/unregister
Title: PushManager.unregister()
on GitHub
Flaw count: 2

• macros:
  • /en-US/docs/Web/API/DOMRequest does not exist
  • /en-US/docs/Web/API/DOMRequest does not exist

---

URL: /en-US/docs/Web/API/PushManager/register
Title: PushManager.register()
on GitHub
Flaw count: 2

• macros:
  • /en-US/docs/Web/API/DOMRequest does not exist
  • /en-US/docs/Web/API/DOMRequest does not exist

---

URL: /en-US/docs/Web/API/PushManager/registrations
Title: PushManager.registrations()
on GitHub
Flaw count: 2

• macros:
  • /en-US/docs/Web/API/DOMRequest does not exist
  • /en-US/docs/Web/API/DOMRequest does not exist

External URLs

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

No external URLs

---

URL: /en-US/docs/Web/API/PushManager/unregister
Title: PushManager.unregister()
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/API/PushManager/register
Title: PushManager.register()
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/API/PushManager/hasPermission
Title: PushManager.hasPermission()
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/API/PushManager/registrations
Title: PushManager.registrations()
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/API/Push_API
Title: Push API
on GitHub

• https://blog.mozilla.org/services/2016/08/23/sending-vapid-identified-webpush-notifications-via-mozillas-push-service/ (1 time) (Note! This may be a new URL 👀)
• https://www.w3.org/TR/capability-urls/ (1 time) (Note! This may be a new URL 👀)

[Rumyra]

Looks great @teoli2003 👍