Spacing issue inside the editor

[briceduclos]

Describe the bug
I created a common layout: a full-width group that contains a main heading and two columns with text and image. Inside the editor, the heading and paragraph blocks inside the columns have unwanted side paddings. And the main heading has no margin-bottom (related to #859).

To Reproduce
Inside the code editor, paste the following code:

<!-- wp:group {"align":"full","backgroundColor":"blue"} -->
<div class="wp-block-group alignfull has-blue-background-color has-background"><div class="wp-block-group__inner-container"><!-- wp:heading {"textAlign":"center"} -->
<h2 class="has-text-align-center">Group Title</h2>
<!-- /wp:heading -->

<!-- wp:columns {"align":"wide"} -->
<div class="wp-block-columns alignwide"><!-- wp:column -->
<div class="wp-block-column"><!-- wp:image {"sizeSlug":"large"} -->
<figure class="wp-block-image size-large"><img src="https://raw.githubusercontent.com/WordPress/twentytwentyone/trunk/assets/images/Reading.jpg" alt=""/></figure>
<!-- /wp:image -->

<!-- wp:heading {"level":3} -->
<h3>Column 1</h3>
<!-- /wp:heading -->

<!-- wp:paragraph -->
<p>Lorem ipsum dolor sit amet, commodo erat adipiscing elit. Sed do eiusmod ut tempor incididunt ut labore et dolore.</p>
<!-- /wp:paragraph --></div>
<!-- /wp:column -->

<!-- wp:column -->
<div class="wp-block-column"><!-- wp:image {"sizeSlug":"large"} -->
<figure class="wp-block-image size-large"><img src="https://raw.githubusercontent.com/WordPress/twentytwentyone/trunk/assets/images/Reading.jpg" alt=""/></figure>
<!-- /wp:image -->

<!-- wp:heading {"level":3} -->
<h3>Column 2</h3>
<!-- /wp:heading -->

<!-- wp:paragraph -->
<p>Integer enim risus, suscipit eu iaculis sed, ullamcorper at metus. Venenatis nec convallis magna, eu congue velit.</p>
<!-- /wp:paragraph --></div>
<!-- /wp:column --></div>
<!-- /wp:columns --></div></div>
<!-- /wp:group -->

[carolinan]

I think the margin for the title is related to #859