Docs: getBlockOrder() - use core/block-editor instead of core/editor

[Soean]

What?

The function getBlockOrder() was moved from editor to block-editor in #13088. So the docs should be updated to avoid a warning.

[github-actions]

Flaky tests detected in 28a91bb.
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/4563759854
📝 Reported issues:

• [Flaky Test] can create template parts via the block placeholder start blank option #49016 in /test/e2e/specs/site-editor/template-part.spec.js
• [Flaky Test] should be able to create an hierarchical post without title support #36939 in specs/editor/plugins/custom-post-types.test.js

[fabiankaegy]

Great catch :)