Fix app/util/util.h to fix lighting app build (#18811)

Currently building lighting app according to README.md fails with:
/home/sag/projects/project-chip/connectedhomeip/examples/lighting-app/esp32/main/DeviceCallbacks.cpp: In member function 'void AppDeviceCallbacks::OnColorControlAttributeChangeCallback(chip::EndpointId, chip::AttributeId, uint8_t*)':
/home/sag/projects/project-chip/connectedhomeip/examples/lighting-app/esp32/main/DeviceCallbacks.cpp:105:9: error: 'emberAfReadServerAttribute' was not declared in this scope
         emberAfReadServerAttribute(endpointId, ColorControl::Id, ColorControl::Attributes::CurrentSaturation::Id, &saturation,
         ^~~~~~~~~~~~~~~~~~~~~~~~~~
/home/sag/projects/project-chip/connectedhomeip/examples/lighting-app/esp32/main/DeviceCallbacks.cpp:105:9: note: maximum limit of 1000 namespaces searched for 'emberAfReadServerAttribute'
/home/sag/projects/project-chip/connectedhomeip/examples/lighting-app/esp32/main/DeviceCallbacks.cpp:105:9: note: suggested alternative: 'emberAfIsStringAttributeType'
         emberAfReadServerAttribute(endpointId, ColorControl::Id, ColorControl::Attributes::CurrentSaturation::Id, &saturation,
         ^~~~~~~~~~~~~~~~~~~~~~~~~~
         emberAfIsStringAttributeType

Include app/util/util.h to fix the build.

examples/lighting-app/esp32/main/DeviceCallbacks.cpp

@@ -26,6 +26,8 @@
 #include "DeviceCallbacks.h"
 #include "LEDWidget.h"
 
+#include <app/util/util.h>
+
 static const char * TAG = "light-app-callbacks";
 
 extern LEDWidget AppLED;