switch to using android-base/file.h instead of android-base/test_utils.h

Test: compile
Bug: 119313545
Change-Id: I4f7ad84743e974b4b4d1d7256088f6c8b749a237
diff --git a/utf8_test.cpp b/utf8_test.cpp
index fcb25c3..472e82c 100644
--- a/utf8_test.cpp
+++ b/utf8_test.cpp
@@ -21,8 +21,8 @@
 #include <fcntl.h>
 #include <stdlib.h>
 
+#include "android-base/file.h"
 #include "android-base/macros.h"
-#include "android-base/test_utils.h"
 #include "android-base/unique_fd.h"
 
 namespace android {