fix(uishell): various console errors

[alisonjoseph]

Fixed various console errors showing up in the stories for UI Shell.

Changelog

Changed

• SideNavLink can't be a child of SideNavMenu, updated to SideNavMenuItem
• Removed isFixed prop that doesn't exists for HeaderMenuButton
• Only pass highContrast to IconButton, not to custom components in HeaderPopover
• Make sure SideNavItems always wraps children for correct html

Testing / Reviewing

Make sure UI Shell still renders as expected

[netlify]

✅ Deploy Preview for carbon-labs-react ready!

Name	Link
🔨 Latest commit	f3dfc8a
🔍 Latest deploy log	https://app.netlify.com/projects/carbon-labs-react/deploys/691c9e03dc5ec7000876acdb
😎 Deploy Preview	https://deploy-preview-915--carbon-labs-react.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 carbon-labs-web-components ready!

Name	Link
🔨 Latest commit	f3dfc8a
🔍 Latest deploy log	https://app.netlify.com/projects/carbon-labs-web-components/deploys/691c9e037b38f70008f83c73
😎 Deploy Preview	https://deploy-preview-915--carbon-labs-web-components.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.