test: use the mixin design a little more

test/lib/locator/shared/main.cpp

@@ -1,7 +1,7 @@
 #include <gtest/gtest.h>
 #include <entt/config/config.h>
 #include <entt/locator/locator.hpp>
-#include "../../../common/boxed_type.h"
+#include "../../../common/value_type.h"
 #include "lib.h"
 
 TEST(Locator, Shared) {