Fix buffer overflow in leadscout hq receive code

The variable block is a 128-byte buffer, but Scout.wifi.client.read was
passed a buffer size of 256, potentially making it overflow the buffer.
This makes the code use sizeof, so the size passed is always correct.

Author: matthijskooijman

ScoutHandler.cpp

@@ -252,7 +252,7 @@ void leadHQHandle(void) {
   }
 
   // get all waiting data and look for packets
-  while(rsize = Scout.wifi.client.read(block, 256)){
+  while(rsize = Scout.wifi.client.read(block, sizeof(block))){
     len = strlen(buffer);
 
     // process chunk of incoming data