v5/docs: reintroduce `outline` for docs code samples, buttons when `:not(:focus-visib...

v5/docs: reintroduce `outline` for docs code samples, buttons when `:not(:focus-visible)` (#36507)

* Remove outline suppression for focused `<pre>`

Sighted keyboard users rely on knowing where their focus is. If the `<pre>` receives focus (so that it can be scrolled by keyboard users, for instance) then it's essential that they know this is the case

* Only suppress outline for buttons when `:not(:focus-visible)`

* Add right-hand margin to pre

avoids having the focus outline awkwardly clipped by the copy button