Remove 'nested instance' for swaps within Salt DS Component and Patterns library

[pseys]

Currently, in components such as Card, where the content area can be toggled on/off to hide or show the 'swap' component we also provide a 'content area' nested instance. In addition the content area toggle the nested instance provides a Swap/Blank option.

Both mechanisms result in the same outcome so are duplicative.

Remove the nested instance wherever Content area is included within the Salt DS components.

[pseys]

@yunjungyeh I raised this issue with Ben who asked me to log it as an issue in GH for you to address at some point. It may be a good idea to do this before the new libraries are released to include as a minor enhancement.