fix: changed grid container for XL breakpoint

[zetareticoli]

Updated the grid container width for XL breakpoint, following the update from UI kit Italia and Bootstrap Italia.

[github-actions]

⚡ Lighthouse report for the home page 🏠

Category	Score
🟠 Performance	52
🟢 Accessibility	100
🟢 Best practices	100
🟢 SEO	100

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Other pages

• /progetto/ 🟠 82 🟢 100 🟢 100 🟢 100
• /norme-e-riferimenti/linee-guida-di-design/ 🟠 81 🟢 100 🟢 100 🟢 100
• /design-system/componenti/ 🟠 81 🟢 98 🟢 100 🟢 92

[Fupete]

@zetareticoli we must wait for the merge and release of this in a new version of BSI (cc @astagi), and we must prepare a new release of UI Kit Italia before merging this. Is this correct?
I think we can schedule this all for next week. For the time being, I will move the discussion to draft.

[Fupete]

Just a reminder: this is approved, but we need to wait BSI and UI Kit Italia fix releases before merging in the next release of the DS alpha.15 scheduled for next week.

[Fupete]

Update: just merged this in Bootstrap Italia. We wait for the new release of BSI (@astagi) and for our new release of UI Kit Italia (@zetareticoli @Fupete) next days before merging.