tls-max.d: this option is only for TLS-using connections

Ref: #5763
Closes #5764

docs/cmdline-opts/tls-max.d

@@ -10,6 +10,9 @@ Help: Set maximum allowed TLS version
 VERSION defines maximum supported TLS version. The minimum acceptable version
 is set by tlsv1.0, tlsv1.1, tlsv1.2 or tlsv1.3.
 
+If the connection is done without TLS, this option has no effect. This
+includes QUIC-using (HTTP/3) transfers.
+
 .RS
 .IP "default"
 Use up to recommended TLS version.