Remove reliance on gutenberg_get_editor_styles()

[dd32]

Describe the bug
As of WordPress/gutenberg#41306 gutenberg_get_editor_styles() is no longer in Gutenberg 13.7 (Released 7hrs ago), but it's used within the Pattern Creator:

pattern-directory/public_html/wp-content/plugins/pattern-creator/pattern-creator.php

Lines 138 to 145 in bd9e577

	$custom_settings = array(
	'postId' => $post_id,
	'siteUrl' => site_url(),
	'postsPerPage' => get_option( 'posts_per_page' ),
	'styles' => gutenberg_get_editor_styles(),
	'__experimentalBlockPatterns' => array(),
	'__experimentalBlockPatternCategories' => array(),
	);

This was noticed via a fatal error in production in the pattern creator on https://wordpress.org/patterns/new-pattern/:
Uncaught Error: Call to undefined function WordPressdotorg\Pattern_Creator\gutenberg_get_editor_styles() in wp-content/plugins/pattern-creator/pattern-creator.php:142

It's worth noting that the removed file, gutenberg/lib/compat/wordpress-5.9/edit-site-page.php IS present in the version of Gutenberg currently in use on the pattern directory.

Unable to reproduce at a glance, but looks like if it's not currently an issue, it will be in a future gutenberg release when that file is removed. reproduced, I had an old Gutenberg version installed on my test site 🤦

To Reproduce
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2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
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Screenshots
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Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6]
• OS: [e.g. iOS8.1]
• Browser [e.g. stock browser, safari]
• Version [e.g. 22]

Additional context
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[dd32]

Noting that in #509 I just copied the function from Gutenberg 13.6 to the Pattern Directory, quick fix to resolve the fatals, requires some more digging to find the Gutenberg replacement function.

[ryelle]

Looks like this was replaced with get_block_editor_theme_styles — I'm not sure why I stuck with the older function when I have updated others, but hopefully this can be a drop-in replacement.