Downgrade TaskScheduler library version to 3.0.0

examples/Scheduler_example27_PlatformIO/platformio.ini

@@ -15,7 +15,7 @@ framework = arduino
 
 [env]
 lib_deps =
-    arkhipenko/TaskScheduler @ ^4.0.0
+    arkhipenko/TaskScheduler @ ^3.0.0
     
 build_flags = 
     ; -D _TASK_TIMECRITICAL