fix battery option parsing

Fix copy&paste mistake, battery should be enabled
for obsolete "battery" option instead of obsolete
"systray" option.

src/tint2conf/properties_rw.c

@@ -898,7 +898,7 @@ void add_entry(char *key, char *value)
 	}
 
 	/* Battery */
-	else if (strcmp(key, "systray") == 0) {
+	else if (strcmp(key, "battery") == 0) {
 		// Obsolete option
 		config_has_battery = 1;
 		config_battery_enabled = atoi(value);
@@ -1464,4 +1464,4 @@ char *get_action(GtkWidget *combo)
 	if (gtk_combo_box_get_active(GTK_COMBO_BOX(combo)) == 10)
 		return "prev_task";
 	return "none";
-}
+}