Jetpack VaultPress Backup

Medium risk: 3 removed classes, 1 removed hook, 1 removed REST route.

• The filter jetpack_wp_admin_newsletter_settings_enabled is no longer fired. Any code hooked to it stops running silently.
• The class Automattic\Jetpack\Connection\Wpcom_Connector was removed. Code that instantiates or extends it will fatal.
• The class Automattic\Jetpack\My_Jetpack\Activitylog was removed. Code that instantiates or extends it will fatal.
• The class Automattic\Jetpack\My_Jetpack\REST_AI was removed. Code that instantiates or extends it will fatal.
• The REST route /jetpack/v4/jetpack-ai-jwt was removed. Integrations calling it will 404.
• The script/style handle wpcom-connector-card is gone. Code that dequeues, or declares a dependency on, that handle is now wrong.
• New external hostnames appear in this release: widgets.wp.com.