man ss: Fix explanation when no options specified

Really by default ss dumps not only TCP sockets but any kind of socket
which is in ESTABLISHED state (TCP/UDP/UNIX).
Signed-off-by: Vadim Kochan <vadim4j@gmail.com>
Reported-by: Miha Marolt <miham@beyondsemi.com>

man/man8/ss.8

@@ -13,7 +13,7 @@ It can display more TCP and state informations than other tools.
 
 .SH OPTIONS
 When no option is used ss displays a list of 
-open non-listening TCP sockets that have established connection.
+open non-listening sockets (e.g. TCP/UNIX/UDP) that have established connection.
 .TP
 .B \-h, \-\-help
 Show summary of options.