Blogging Prompts Dashboard Card: don't show remove menu item.

[ScoutHarris]

Ref: #18429, #18250, p1652262324746539-slack-C01CW1VMLAF

Per the referenced Slack conversation, the Remove from dashboard option on the dashboard prompt card is removed as it probably won't be implemented for V1.

To test:

• Run on an iOS 14+ device.
• Go to My Site > Home > Prompts.
• Tap on the ellipsis menu.
• Verify Remove from dashboard does not appear.
• Repeat on an iOS 13 device.

iOS 15 Before	iOS 15 After

iOS 13 Before	iOS 13 After

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 Jetpack from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr18627-377da1e on your iPhone

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

[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 pr18627-377da1e on your iPhone

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

[dvdchr]

Tested in both iOS 15 and 13. LGTM. The remove button is removed!

[ScoutHarris]

Thanks @dvdchr !