SmartFrame block: works on WordPress.com (simple sites) but not self-hosted

### Impacted plugin

Jetpack

### Quick summary

The SmartFrame embed block works on WordPress.com for simple sites but not with atomic sites or Jetpack on self-hosted.

### Steps to reproduce

1. Create a test site on either self-hosted or atomic site on WordPress.com
2. Add a SmartFrame block, and embed https://support.smartframe.io/p/imgp7068_3_copy_1676383547359/628c192e4f448e34f5c451a37dd16ab3 (example from https://smartframe.io/)

### A clear and concise description of what you expected to happen.

Embedded image showing in the editor and live preview.

### What actually happened

Embed doesn't display on the live preview.

Here are more detailed notes from different hosting:

#### Jurassic Ninja
Error message: `Sorry, this content could not be embedded.`

#### Atomic site

Embed doesn't display in the editor, but displays on the live site.

#### Jetpack on self-hosted

Embed displays neither in the editor or live site.

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For Atomic and Jetpack on self-hosted, the editor show this error:

### Impact

Most (> 50%)

### Available workarounds?

Yes, easy to implement

### Platform (Simple and/or Atomic)

Self-hosted

### Logs or notes

SmartFrame guide to embed on WordPress, it recommends using an HTML block to add the script to embed. https://smartframe.io/support/embed-smartframe-on-wordpress/

SmartFrame block was previously fixed in https://github.com/Automattic/jetpack/issues/21062.

Context: ran into this while updating some docs and testing the Jetpack blocks.

Start by reproducing the SmartFrame block on a self-hosted site and an Atomic site, comparing both with WordPress.com simple sites. Read the SmartFrame embedding guide and prior issue #21062, then verify that the embed appears in both the editor and live preview across the affected hosting types.

Written by the indexing model from the issue text.