Remove unused includes in tilingtest,utilstest

tests/gtest/aviftilingtest.cc

diff --git a/tests/gtest/aviftilingtest.cc b/tests/gtest/aviftilingtest.cc
index b828216..c83e6a7 100644
--- a/tests/gtest/aviftilingtest.cc
+++ b/tests/gtest/aviftilingtest.cc
@@ -3,7 +3,6 @@
 
 #include <ostream>
 
-#include "avif/avif.h"
 #include "avif/internal.h"
 #include "gtest/gtest.h"
 

tests/gtest/avifutilstest.cc

diff --git a/tests/gtest/avifutilstest.cc b/tests/gtest/avifutilstest.cc
index fe342f4..4dfc96d 100644
--- a/tests/gtest/avifutilstest.cc
+++ b/tests/gtest/avifutilstest.cc
@@ -3,9 +3,7 @@
 
 #include <cmath>
 
-#include "avif/avif.h"
 #include "avif/internal.h"
-#include "aviftest_helpers.h"
 #include "gtest/gtest.h"
 
 namespace libavif {