test: increase coverage for http2 response headers

Expanded an existing test for setting pseudo-headers on response to
include all pseudo-headers, not just :status.

PR-URL: https://github.com/nodejs/node/pull/15035
Refs: https://github.com/nodejs/node/issues/14985


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>