Cleanup responsive tables

Created by: MartijnCuppens

In https://github.com/twbs/bootstrap/pull/25058, the .table-reponsive class was moved from the table to a wrapper div.

• display: block; and width: 100%; have become redundant since the wrapper is a div
• The double border fix isn't needed either since the table keeps its display value
• I've also simplified the Sass class concatenation.

https://deploy-preview-30482--twbs-bootstrap.netlify.com/docs/4.3/content/tables/#breakpoint-specific