audio_core: Remove unnecessary inclusions

Same behavior, but removes header dependencies where they don't need to
be.

src/audio_core/stream.cpp

@@ -12,7 +12,6 @@
 #include "common/assert.h"
 #include "common/logging/log.h"
 #include "core/core_timing.h"
-#include "core/core_timing_util.h"
 #include "core/settings.h"
 
 namespace AudioCore {