fix(docs): move spacings migration tip on top of the paragraph in migration from boosted

[MaxLardenois]

Description

Put the spacings migration tips at the start of the spacings paragraph in migration from boosted.

Checklists

• I have read the contributing guidelines
• My change follows the developer guide
• My change follows the page structure defined in [OUDS] Create a component page template for the doc #3045
• Title and DOM structure is correct
• Links have been updated (title change impacts links for example)

Progression (for Core Team only)

• Code review
• Commit on ouds/main following conventional commit

Live previews

• https://deploy-preview-3304--boosted.netlify.app/

[netlify]

✅ Deploy Preview for boosted ready!

Name	Link
🔨 Latest commit	65cf7fb
🔍 Latest deploy log	https://app.netlify.com/projects/boosted/deploys/69529ae969cab10008a46dd8
😎 Deploy Preview	https://deploy-preview-3304--boosted.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[netlify]

✅ Deploy Preview for boosted ready!

Name	Link
🔨 Latest commit	ccd0bfa
🔍 Latest deploy log	https://app.netlify.com/projects/boosted/deploys/69529afc5ec4b20008b75fad
😎 Deploy Preview	https://deploy-preview-3304--boosted.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.