tools: remove @babel/plugin-syntax-import-assertions

As of ESLint 8.0.0 at least, this plugin is unnecessary.

PR-URL: https://github.com/nodejs/node/pull/40394


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>