Change PSCP's default protocol to SSH.

Apparently it's been set on Telnet for the entire lifetime of PSCP. It
can't have caused any trouble, or we'd have noticed by now, but it
still seems silly to set it to something that PSCP clearly can't
handle!

pscp.c

@@ -2229,7 +2229,7 @@ int psftp_main(int argc, char *argv[])
     int i;
     bool sanitise_stderr = true;
 
-    settings_set_default_protocol(PROT_TELNET);
+    settings_set_default_protocol(PROT_SSH);
 
     sk_init();