http2: fix reinjection check

We reinject when the sockets has already waiting
data, remarked by @mildsunrise

Co-authored-by: Alba Mendez <me@alba.sh>

PR-URL: https://github.com/nodejs/node/pull/35678


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Alba Mendez <me@alba.sh>
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Ricky Zhou <0x19951125@gmail.com>