fix(ios, messaging): remove UNNotificationServiceExtension in favour of local target extension

[davidepalazzo]

Description

As covered in #4218 I'm removing the code I added with #4085 as it seems it isn't stable enough.

The new additional documentation added with #4225 will provide a better way to enable images in messaging. More details on the reason for this change can be seen on the Apple's documentation about Notification Extension.

Related issues

#4218

Release Summary

Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
  • Yes
• My change supports the following platforms;
  • Android
  • iOS
• My change includes tests;
  • e2e tests added or updated in packages/\*\*/e2e
  • jest tests added or updated in packages/\*\*/__tests__
• I have updated TypeScript types that are affected by my change.
• This is a breaking change;
  • Yes
  • No

Test Plan

---

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[mikehardy]

working on the docs PR but this looks good as a companion to it