README: Remove client only restriction for QUIC.

README: Remove client only restriction for QUIC.

The QUIC protocol is also supported on server side.
Update the README file accordingly.

Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
Reviewed-by: Neil Horman <nhorman@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/27258)

(cherry picked from commit 648366ad010b3b22c1f298d39934d72702b3fd55)