Subscriptions: padding issues with Group block in emails

> The email notification for this post shows the grey background boxes, like the one for w00t Dev Docs, as having no padding like we see here.

On the site:

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Reported here:
https://wptavern.com/woocommerce-releases-8-6-8-6-1#comment-450172

No implementation files or tests are named. Start by reproducing the subscription email for a post containing a Group block and compare its grey background boxes with the corresponding on-site rendering and the linked report. Done means the email preserves the Group block's expected padding.

Written by the indexing model from the issue text.