[FIX] pfe-tabs on horizontal earth have double border

[alazzara]

Description of the issue

PFE-tabs has a double border on the horizontal earth variant. It seems like this is because the tabs have #b8bbbe as the bottom border, and the .tabs container has border-bottom #d2d2d2 (both hexes are fallback colors)

Impacted component(s)

• PFE-tabs

Steps to reproduce

1. Go to '/elements/pfe-tabs/demo/'
2. Scroll to 'horizontal wind variant section'
3. notice the tabs have a border as well as the .tabs container. Which is causing a double border

Expected behavior

I should only see border on either the tab of the .tabs container not both. Tabs should not appear to have double borders.

Screenshots