Remove Adding an Apple Watch extension page

[jmagman]

Description of what this PR is changing or adding, and why:

"Adding an Apple Watch extension" page only has two instructions--turn on bitcode, and add the extension. I need to delete the "turn on bitcode" step 1 since Apple has deprecated bitcode flutter/flutter#107887. That leaves a very low-quality page. Delete it.

Issues fixed by this PR (if any): Part of flutter/flutter#107887

Presubmit checklist

• This PR doesn’t contain automatically generated corrections (Grammarly or similar).
• This PR follows the Google Developer Documentation Style Guidelines — for example, it doesn’t use i.e. or e.g., and it avoids I and we (first person).
• This PR uses semantic line breaks of 80 characters or fewer.

[sfshaza2]

I was recently looking at this page and I knew that the bitcode info needed to be removed and I was wondering how we'd do that, so I think this IS the best option. Besides, we ultimately need more generalized info on how to deal with embedded functionality.