Replace 'should_skip_block_supports_serialization' with the core utility method

[Mamaduka]

What?

PR replace gutenberg_should_skip_block_supports_serialization with wp_should_skip_block_supports_serialization.

Why?

The plugin now requires a minimum WP 6.0, so we can remove the gutenberg_should_skip_block_supports_serialization compat layer.

Testing Instructions

1. Downgrade WP installation to WP 6.0 - wp core update --version=6.0.3 --force
2. Confirm there are no fatal errors when visiting the testing site - frontend and the editor.

[github-actions]

Flaky tests detected in b3ee252.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/3931615590
📝 Reported issues:

• [Flaky Test] should select by dragging into nested block #44673 in specs/editor/various/multi-block-selection.test.js

[ntsekouras]

💯