Full Site Editing: Fix editor frame after a Gutenberg update

[Copons]

Changes proposed in this Pull Request

• Update a block editor editor CSS class name that was changed in a recent Gutenberg update.

Note: this must be deployed AFTER Gutenberg 7.0.0 lands on WPCOM (see p7DVsv-7Ks-p2).

Testing instructions

• This must be tested on a FSE site with an updated Gutenberg, or on Horizon.
• Open the page editor and make sure the FSE frame is visible.
• Add blocks with different widths (regular, wide, full), and check if they adapt to the frame width instead of the full editor width.
• Repeat the previous tests in the template part editor.

Fixes #37837

[matticbot]

Test live: https://calypso.live/?branch=fix/37837-fse-editor-frame

[matticbot]

This PR does not affect the size of JS and CSS bundles shipped to the user's browser.

Generated by performance advisor bot at iscalypsofastyet.com.

[Addison-Stavlo]

I just tested these changes on Horizon, it looks good and works well.

Side Note: Is there a reason why this frame is important to us for FSE, while it seems to be non-existant for non-FSE editor?

[Copons]

I just tested these changes on Horizon, it looks good and works well.

Thanks!

Side Note: Is there a reason why this frame is important to us for FSE, while it seems to be non-existant for non-FSE editor?

There are many reasons! 🙂
One is that, especially for template parts, it's jarring to see them on a huge white canvas, when they are supposed to be only a piece of the page.
I think it's more obvious when you see them side by side:

Vanilla	FSE Frame