Spacing: replace var() format with var:preset|spacing|value

[carolinan]

Across the templates, the format var(--wp--preset--spacing--90) is used inside the JSON block comment. For the code in the template to match the code of new blocks added in the block editor, this format should be used: var:preset|spacing|numeric-value See https://github.com/WordPress/twentytwentythree/pull/55#discussion_r952127903

[carolinan]

Updating it for the spacer block did not work:

<!-- wp:spacer {"height":"var:preset|spacing|40"} -->
<div style="height:var(--wp--preset--spacing--40)" aria-hidden="true" class="wp-block-spacer"></div>
<!-- /wp:spacer -->

Block validation failed for `core/spacer` (Object).
Content generated by `save` function:
<div style="height:var:preset|spacing|40" aria-hidden="true" class="wp-block-spacer"></div>
Content retrieved from post body:
<div style="height:var(--wp--preset--spacing--40)" aria-hidden="true" class="wp-block-spacer"></div>

[mikachan]

It looks like we've replaced all the possible spacing presets with the correct format across the templates.

The only ones left are the spacer blocks, but it looks like this currently isn't possible as the spacing presets are not valid height settings. I've opened up an issue for this: https://github.com/WordPress/gutenberg/issues/43816