doc: make small improvements to REPL doc

* button -> key
* apply missing kbd element
* revise "Recoverable errors" text for brevity and clarity

PR-URL: https://github.com/nodejs/node/pull/35808


Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>