ssl-opt.sh: Fix "no TLS 1.3 server support" test check

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index b18f3cf..c35d5da 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -9625,7 +9625,7 @@
             "$P_SRV debug_level=2 force_version=tls13" \
             "$P_CLI debug_level=2 force_version=tls13" \
             1 \
-            -s "TLS 1.3 server is not supported yet."
+            -s "The requested feature is not available"
 
 requires_openssl_tls1_3
 requires_config_enabled MBEDTLS_SSL_PROTO_TLS1_3