Bottom border under breadcrumbs is too distracting

[SnosMe]

Does this issue occur when all extensions are disabled?: Yes/No

• VS Code Version: 1.111.0
• OS Version:

Steps to Reproduce:

1. Theme "Light+"
2. Observe distracting line under breadcrumbs. Before this update there were none, and only shadow appeared when you scroll.

From #299275

verify breadcrumbs have a subtle bottom border

I don't know what definition of "subtle" you are using.