Update build-instructions-openbsd.md

[Lutitious]

Switch openbsd instructions to qt6 as it appears to work fine.

Still need to test mc itself on metal since this was in a vm so leaving as a draft for now.

Goal longterm is to maintain an actual prismlauncher package for openbsd

[netlify[bot]]

✅ Deploy Preview for prismlauncher ready!

Name	Link
🔨 Latest commit	f69fae43337ad4121b9b1e54bc501a4775bb989b
🔍 Latest deploy log	https://app.netlify.com/sites/prismlauncher/deploys/668c974cf1d3be00081fb9de
😎 Deploy Preview	https://deploy-preview-496--prismlauncher.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.
Lighthouse	1 paths audited Performance: 100 (no change from production) Accessibility: 97 (no change from production) Best Practices: 100 (no change from production) SEO: 92 (no change from production) PWA: - View the detailed breakdown and full score reports

---

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