Comment out freeMemory function declaration

Comment out the freeMemory function declaration.

examples/Scheduler_example19_Dynamic_Tasks_stdQueue/Scheduler_example19_Dynamic_Tasks_stdQueue.ino

@@ -19,7 +19,7 @@
 
 #include <queue>
 
-int freeMemory();
+// int freeMemory();
 
 #if defined (ARDUINO_ARCH_AVR)
 #include <MemoryFree.h>