themes-wordpress/blockbase/sass/base/_text.scss

// Needed until https://github.com/WordPress/gutenberg/issues/35267 is resolved.
p.wp-block.wp-block-paragraph, // This selector has been made extra specific to override the block gap being set in the editor.
*[class^="wp-container"] > * + p,
*[class^="wp-container"] > p + *,
p {
	margin-top: 1em;
}