Raise the timeout in quic_client_test.c

Raise the timeout in quic_client_test.c

Recently the Coveralls CI run started failing
because it times out in this test.
Outside of Coveralls it runs fine so assuming that
this is caused by slow execution under Coveralls.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21844)