Docs: Fix broken links in Gutenberg release checklist

[t-hamano]

What?

Follow-up #71130

We split the Gutenbberg Release Process page into subpages. As a result, the anchor links in the Gutenberg release checklist no longer work. This PR correctly updates these links.

Testing Instructions

Access the updated links and confirm that they are linked to the appropriate sections.

[github-actions]

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Co-authored-by: t-hamano <[email protected]>
Co-authored-by: priethor <[email protected]>
Co-authored-by: Mamaduka <[email protected]>

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[github-actions]

Flaky tests detected in 2c41b8a.
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/17644076434
📝 Reported issues:

• [Flaky Test] Focus management when creating navigation links #71108 in /test/e2e/specs/editor/blocks/navigation.spec.js
• [Flaky Test] ensures List View global shortcut works properly #51533 in /test/e2e/specs/editor/various/list-view.spec.js
• [Flaky Test] should refresh the page when stylesheet loading fails #71135 in /test/e2e/specs/interactivity/router-styles.spec.ts

[priethor]

Links are working 🚀

[Mamaduka]

Thanks, @t-hamano!