test: http2-respond-file-errors to fixtures module

Replace common.fixturesDir with fixtures in
test-http2-respond-file-errors.js.

PR-URL: https://github.com/nodejs/node/pull/16004


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>