Update super sidebar counter styles to have 32px height

What does this MR do and why?

Update super sidebar counter styles to have 32px height

• Add temp gl-inset-border-1-gray-a-08 class to super_sidebar.scss
• Add line-height:normal to <counter>
• Add box-shadow: none on :hover/:focus

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Enable the feature flag in rails console with rails c

Feature.enable(:super_sidebar_nav)

• Enable the "New navigation" setting toggle from the user dropdown

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #393131 (closed)