Video Block: Migrate over default block styles as theme.json settings

[scruffian]

These are the video block styles:

.wp-block-video {

	figcaption {
		color: var(--global--color-primary);
		font-size: var(--global--font-size-xs);
		margin-top: calc(0.5 * var(--global--spacing-unit));
		margin-bottom: var(--global--spacing-unit);
		text-align: center;
	}
}

I don't think we need to migrate these styles as Gutenberg already has them.

* > figure > video {
	max-width: unset;
	width: 100%;
	vertical-align: middle;
}

The bottom styles are being migrated to Gutenberg: WordPress/gutenberg#27328

Broken out of #82

[scruffian]

WordPress/gutenberg#27328 is merged so I think we can close this and mark the video block as done. @kjellr does that make sense to you?

[kjellr]

Yeah, that sounds good to me!