Minor docs improvements (#1774) (#1775)

* Fix some botched formatting (replace ```mdoc scala with ```scala mdoc)
* Replace some unnecessary uses of triple backticks with single
  backticks
* Move appendix docs from wiki-deprecated/ to appendix/
  * This will require an update on the website as well
* Update Bundle literal docs

(cherry picked from commit 8fa46071

)

Co-authored-by: Jack Koenig <koenig@sifive.com>