doc: remove spaces around slashes

Remove spaces around slash characters in documentation. This change
sometimes rewords the content where the slash construction may not be
what is called for.

PR-URL: https://github.com/nodejs/node/pull/21140


Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>