Stats: Remove legacy widget loader from WP Admin

[dognose24]

Fixes #40412

Proposed changes:

• Remove the legacy Stats widget loader to prevent seeing the outdated Stats widget when visiting /wp-admin of Simple sites with the Default Admin interface style.
• Ignore the enable_odyssey_stats option for the WPAdmin Dashboard widget completely.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

No.

Testing instructions:

• Launch a Simple site and go to the WPCOM Settings page: https://wordpress.com/settings/general/{site-slug}.
• Ensure the Admin interface style is set to Default style.
• Visit the Simple site WPAdmin Dashboard: https://{site-slug}/wp-admin.
• Ensure the legacy Stats widget is not shown anymore.

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the update/stats_remove_legacy_widget_loader branch.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack update/stats_remove_legacy_widget_loader
  

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

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Jetpack plugin:

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[kangzj]

The PR seems only to fix Atomic and Jetpack sites. For simple sites, I'm still seeing the legacy widget Admin set to Calypso, and access WP-Admin directly:

[kangzj]

Ah the widget is loaded here for Simple Sites:

jetpack/projects/packages/jetpack-mu-wpcom/src/features/wpcom-simple-odyssey-stats/wpcom-simple-odyssey-stats.php

Line 17 in be744e8

add_action( 'wp_dashboard_setup', array( new Jetpack_Stats_Dashboard_Widget(), 'init' ) );

So it'll work when the mu plugin is updated, so I think Simple sites will be fixed by the PR as well. 👍