android: Cleanup unneeded headers from the sync stub

These were probably copy pasted from the previous unified stub.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Helen Koike <helen.koike@collabora.com>
Reviewed-by: Sergi Blanch Torné <sergi.blanch.torne@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20019>

src/android_stub/sync_stub.cpp

@@ -1,8 +1,4 @@
-#include <cutils/properties.h>
 #include <sync/sync.h>
-#include <hardware/hardware.h>
-#include <android/log.h>
-#include <backtrace/Backtrace.h>
 
 extern "C" {