doc: use a single space between sentences

We mostly have a single space between the punctuation that ends a
sentence and the start of the next sentence. Change instances with two
spaces to one.

PR-URL: https://github.com/nodejs/node/pull/33995


Reviewed-By: Matheus Marchini <mat@mmarchini.me>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>