tools: make trailing commas consistent in .eslintrc

.eslintrc has lots of trailing commas and lots of places where there
aren't trailing commas. Use trailing commas throughout the files for
consistency.

PR-URL: https://github.com/nodejs/node/pull/25739


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>