pw_preprocessor: Reduce util_test.cc stack usage

This fixes a warning if compiling with -Wframe-larger-than=N for N <
6622896.

Change-Id: Ica3b5418c60570c11d411805e3d4c6efac8ab7e9
diff --git a/pw_preprocessor/util_test.cc b/pw_preprocessor/util_test.cc
index 50b5cf1..05771a0 100644
--- a/pw_preprocessor/util_test.cc
+++ b/pw_preprocessor/util_test.cc
@@ -31,13 +31,13 @@
 
   struct Object {
     int a;
-    uint64_t array[2048];
+    uint64_t array[7];
   };
-  Object objects[404];
+  Object objects[9];
 
-  static_assert(PW_ARRAY_SIZE(objects) == 404);
-  static_assert(PW_ARRAY_SIZE(Object::array) == 2048);
-  static_assert(PW_ARRAY_SIZE(objects[1].array) == 2048);
+  static_assert(PW_ARRAY_SIZE(objects) == 9);
+  static_assert(PW_ARRAY_SIZE(Object::array) == 7);
+  static_assert(PW_ARRAY_SIZE(objects[1].array) == 7);
 }
 
 TEST(Macros, UnusedVariable) {