Blogging Prompts: Add check to prompts header to only display for WP sites

[wargcm]

See: #18429

Description

Hides the prompts action sheet header view on self-hosted sites.

Testing

To test:

• Enable bloggingPrompts feature flag in FeatureFlag.swift
• Launch the app and sign in if necessary
• Select a WP hosted site
• Navigate to the 'My Site' tab
• Tap on the floating action button '+'
• Verify the prompts header is still shown
• Switch to a self-hosted site or mock the return of that bool
• Tap on the floating action button '+'
• Verify the prompts header is hidden

Regression Notes

1. Potential unintended areas of impact
   N/A

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   N/A

3. What automated tests I added (or what prevented me from doing so)
   N/A

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

You can test the changes in WordPress from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr18819-085d75b on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[wpmobilebot]

You can test the changes in Jetpack from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr18819-085d75b on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[alpavanoglu]

Hey Chris 👋
The prompt does not appear for our internal store. Is that intended?

[wargcm]

Posting here as well just in case anyone comes across this PR. We discussed this in Slack.

I'm actually not sure if our internal site is hosted by a 3rd party or if it's the case the internal sites are not accessible by our API's. I'm assuming one of the two is the case.

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Thanks for the review @alpavanoglu!