Fix full-width container editor padding in WP 5.5

[nickcernis]

Ensures that full width container, pricing, and advanced column blocks do not have additional padding in the editor under WordPress 5.5.

Applies the same fix @dreamwhisper made to Genesis Blocks in https://github.com/studiopress/genesis-blocks/pull/45.

Fixes #395.

How to test

Under WP 5.5+.

1. Add a container, pricing, and advanced column block.
2. Set each to full-width.
3. In the editor, check that there is not excessive padding to the left and right of the blocks.

Suggested changelog entry

• Removed unnecessary padding in the editor on full-width Container, Pricing, and Advanced Column blocks.