src:arduino-timer: use task_id in cancel

Use task_id in cancel to simplify the check and remove the confusing
cast.

Author: contrem

src/arduino-timer.h

@@ -94,7 +94,7 @@ class Timer {
         if (!task) return;
 
         timer_foreach_task(t) {
-            if (t->handler && (t->id ^ task) == (uintptr_t)t) {
+            if (t->handler && task_id(t) == task) {
                 remove(t);
                 break;
             }