docs(jump-links): fix scrollspy demo layout

[bennypowers]

What I did

1. adjust the demo page css to fix the horizontal jump links layout

   Testing instructions

• https://deploy-preview-2721--patternfly-elements.netlify.app/components/jump-links/demo/scrollspy-with-subsections
• toggle horizontal
• observe that page layout adjusts as needed

Closes #2719

[changeset-bot[bot]]

⚠️ No Changeset found

Latest commit: 38fcdd99ae38db555993a11554e96fd096b48959

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[github-actions[bot]]

✅ Deploy Preview for patternfly-elements ready!

Name	Link
🔨 Latest commit	6e8638bd3adcd1c305c8e0c4bdd640db87a3f80a
😎 Deploy Preview	https://deploy-preview-2721--patternfly-elements.netlify.app/

---

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

[netlify[bot]]

✅ Deploy Preview for patternfly-elements ready!

Name	Link
🔨 Latest commit	38fcdd99ae38db555993a11554e96fd096b48959
🔍 Latest deploy log	https://app.netlify.com/sites/patternfly-elements/deploys/660586e31347f700085a8879
😎 Deploy Preview	https://deploy-preview-2721--patternfly-elements.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 site configuration.