For now, only define:
- @font-family-sans (unused in MinervaNeue, but for possible future use)
- @border-radius-base
With current implementation before this patch, MinervaNeue is relying on core's default
`@border-radius` which is set to `0` to be close to HTML default.
MinervaNeue is currently not applying correct skin's `border-radius`.
Bug: T263270
Change-Id: I9a149eefd15efede27416ada4db07072e53628ec
