Removed explicit height on sidebar

[lamATnginx]

Proposed changes

Removes height of 100vh from sidebar as it is making the page longer than needed as seen in a page such as http://localhost:1313/nginx-gateway-fabric/reference/technical-specifications/

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• I have read the CONTRIBUTING document
• If applicable, I have added tests that prove my fix is effective or that my feature works
• If applicable, I have checked that any relevant tests pass after adding my changes
• I have updated any relevant documentation (README.md and CHANGELOG.md)