Premium Content: Remove premium content block placeholder

[apeatling]

Changes proposed in this Pull Request

Do not use a placeholder when the user is not on the required plan. Allow them to see and edit content. This will allow patterns to render for folks without a plan.

This PR should be merged along with Automattic/jetpack#17702 to allow the payments block to be interacted with without a plan.

Before
Only showing placeholder:

After
Showing editable content:

Testing instructions

• Check out this branch
• Sync to your sandbox using yarn dev --sync
• Insert a Premium Content block on your sandboxed site (that has a free plan) and confirm you can edit content.
• Save and reload the editor and confirm changes are saved
• Open the front end of the site and confirm that no content is visible. This will be fixed in https://github.com/Automattic/view-design/issues/95 and https://github.com/Automattic/view-design/issues/127

Fixes https://github.com/Automattic/view-design/issues/124

[matticbot]

Test live: https://calypso.live/?branch=remove/premium-content-placeholder

[matticbot]

Caution: This PR affects files in the Editing Toolkit Plugin on WordPress.com
Please ensure your changes work on WordPress.com before merging.

D52241-code has been created so you can easily test it on your sandbox. See this FieldGuide page about developing the Editing Toolkit Plugin for more info: PCYsg-ly5-p2

[stacimc]

Tested and confirmed that the Premium Content block loads with editable content on a free plan, but does not display on the frontend. I still see the jetpack recurring payments disclaimer, which is causing some odd styling, but it looks like that will be removed with the jetpack PR you linked -- so looks good to me.

Approving because I think this is intended, but I did have a question: The upgrade banner only displays when the top-level Premium Content block is selected (meaning if you click out of the block or into an inner block, it disappears and the warning is no longer visible). I think this is expected behavior for upgrade banners, but just calling out as a potential source of confusion.