test: revert undesired debug change in ssl-opt

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/tests/ssl-opt.sh b/tests/ssl-opt.sh
index 12dcdbc..2bbd34a 100755
--- a/tests/ssl-opt.sh
+++ b/tests/ssl-opt.sh
@@ -5759,7 +5759,7 @@
 
 requires_config_enabled MBEDTLS_X509_TRUSTED_CERTIFICATE_CALLBACK
 run_test    "Authentication, CA callback: server ECDH p256v1, client optional, p256v1 unsupported" \
-            "$P_SRV debug_level=4 key_file=data_files/server5.key \
+            "$P_SRV debug_level=1 key_file=data_files/server5.key \
              crt_file=data_files/server5.ku-ka.crt" \
             "$P_CLI force_version=tls12 ca_callback=1 debug_level=3 auth_mode=optional curves=secp521r1" \
             1 \