Remove recommendations of Firebase Studio

[delucis]

Description (required)

Firebase Studio is being sunset and is no longer recommended for new projects (see “Firebase Studio sunset and project migration”).

This PR:

• removes mentions of Firebase Studio where we talk about astro.new (in preparation for removing Firebase Studio there too)
• updates our tutorial to recommend StackBlitz instead as the in-browser IDE option

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Tracked Files

File	Note
en/editor-setup.mdx	Source changed, localizations will be marked as outdated.
en/guides/cms/builderio.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-docusaurus.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-eleventy.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-gatsby.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-gitbook.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-gridsome.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-hugo.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-jekyll.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-nextjs.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-nuxtjs.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-pelican.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-sveltekit.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-vuepress.mdx	Source changed, localizations will be marked as outdated.
en/guides/migrate-to-astro/from-wordpress.mdx	Source changed, localizations will be marked as outdated.
en/tutorial/0-introduction/index.mdx	Source changed, localizations will be marked as outdated.
en/tutorial/1-setup/index.mdx	Source changed, localizations will be marked as outdated.
en/tutorial/6-islands/3.mdx	Source changed, localizations will be marked as outdated.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.

[louisescher]

LGTM!

[ArmandPhilippot]

I checked the preview too for the tutorial, LGTM!

To think I did almost the same thing not long ago... they could have made up their minds sooner #13337 😆