test: remove flaky designation for test-http2-large-file

This seems to have stopped happening, possibly because it only ever
happened on win2008 and that went eol last year.

Closes: https://github.com/nodejs/node/issues/22327

PR-URL: https://github.com/nodejs/node/pull/37156
Fixes: https://github.com/nodejs/node/issues/22327


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Stephen Belanger <admin@stephenbelanger.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>