Storybook: Fix storybook blocks imports

[tyxla]

What?

Fixes a deprecated import warning in a few stories.

Why?

Just fixing some deprecated import warnings.

Found while working on #67574.

How?

We're using @storybook/blocks instead of @storybook/addon-docs/blocks.

Testing Instructions

• Verify that there is no deprecated import warning in the console of the following pages in Storybook:
  • Tokens: Elevation: http://localhost:50240/?path=/docs/tokens-elevation--page
  • Tokens: Typography: http://localhost:50240/?path=/docs/tokens-typography--page
  • Design language: Radius: http://localhost:50240/?path=/docs/foundations-design-language-radius--page
  • Design Language: Elevation: http://localhost:50240/?path=/docs/foundations-design-language-elevation--page

Testing Instructions for Keyboard

Same

Screenshots or screencast

Error before this PR:

[github-actions]

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Co-authored-by: tyxla <tyxla@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>

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[github-actions]

Flaky tests detected in e0e3ebb.
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/12196918036
📝 Reported issues:

• [Flaky Test] Redirection after template creation #60678 in /test/e2e/specs/site-editor/site-editor-url-navigation.spec.js