Fix watchdog code in repeater

src/helpers/ExWatchdogManager.h

@@ -1,8 +1,9 @@
 #pragma once
 
 class ExWatchdogManager {
-public:
+protected:
   unsigned long next_feed_watchdog;
+public:
   ExWatchdogManager() { next_feed_watchdog = 0; }
   virtual bool begin() { return false; }
   virtual void loop() { }