rdp: Silence compiler warning

This value is always `NULL`.

Silences:
`warning: ‘%s’ directive argument is null [-Wformat-overflow=]`

Signed-off-by: Robert Mader <robert.mader@collabora.com>

libweston/backend-rdp/rdp.c

@@ -863,9 +863,9 @@ convert_rdp_keyboard_to_xkb_rule_names(UINT32 KeyboardType,
 		xkbRuleNames->variant = 0;
 	}
 
-	weston_log("%s: matching model=%s layout=%s variant=%s options=%s\n",
+	weston_log("%s: matching model=%s layout=%s variant=%s\n",
 		   __func__, xkbRuleNames->model, xkbRuleNames->layout,
-		   xkbRuleNames->variant, xkbRuleNames->options);
+		   xkbRuleNames->variant);
 }
 
 static BOOL