extras: update include file

Author: contrem

extras/tests/rollover-generic/rollover-generic.ino

@@ -2,7 +2,7 @@
  Test timer rollover handling
  */
 
-#include <timer.h>
+#include <arduino-timer.h>
 
 unsigned long wrapping_millis();
 

extras/tests/rollover/rollover.ino

@@ -3,7 +3,7 @@
  */
 
 #include <util/atomic.h>
-#include <timer.h>
+#include <arduino-timer.h>
 
 auto timer = timer_create_default();