feat: minor fixes to maintain ui consistency

[askayastha22]

Description

1. Deleting a variant automatically moves the selection to the first variant.
2. Heading of Favorites panel is now consistent with theNew Session panel.

Preview: https://experience.adobe.com/?shell_source=dev&ref=genai-plugin-dev&repo=wknd&owner=hlxsites&project=WKND#/@sitesinternal/aem/generate-variations/

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.