Remove code that relies on v4 cookie redirects

[tylerlwsmith]

Description (required)

Astro 5 removed introduced a breaking change where failed actions no longer redirect back to the page where a form was submitted.

This PR modifies an "actions" example that relied on the v4 behavior, making it work with Astro v5.

Related issues & labels (optional)

• Closes N/A
• Suggested label: code snippet update

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Tracked Files

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en/guides/actions.mdx	Source changed, localizations will be marked as outdated.

Warnings reference

Icon	Description
🔄️	The source for this localization has been updated since the creation of this pull request, make sure all changes in the source have been applied.

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