jetpack Social: Clean up media auto-conversion backend logic

Following #38497, #38499, we need to clean up the unused backend logic for auto-conversion

Proposed changes:

Remove the backend logic for auto-conversion

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?

Testing instructions:

Just do a smoke test for Social admin, Jetpack settings and Editor pages

Jul 29 '24 13:07 manzoorwanijk

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/social/clean-up-media-auto-conversion-backend-logic branch.
- For jetpack-mu-wpcom changes, also add define( 'JETPACK_MU_WPCOM_LOAD_VIA_BETA_PLUGIN', true ); to your wp-config.php file.

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

bin/jetpack-downloader test jetpack update/social/clean-up-media-auto-conversion-backend-logic

bin/jetpack-downloader test jetpack-mu-wpcom-plugin update/social/clean-up-media-auto-conversion-backend-logic

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

Jul 29 '24 13:07 github-actions[bot]

Thank you for your PR!

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