lib: fix typo in lib/internal/http2/core.js

PR-URL: https://github.com/nodejs/node/pull/37695


Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>