Get duration_t in printcounter.h for its clients (#9843)

Marlin/src/module/printcounter.cpp

@@ -27,7 +27,6 @@
 #include "printcounter.h"
 
 #include "../Marlin.h"
-#include "../libs/duration_t.h"
 
 PrintCounter::PrintCounter(): super() {
   this->loadStats();

Marlin/src/module/printcounter.h

@@ -25,6 +25,7 @@
 
 #include "../inc/MarlinConfig.h"
 #include "../libs/stopwatch.h"
+#include "../libs/duration_t.h"
 
 // Print debug messages with M111 S2
 //#define DEBUG_PRINTCOUNTER