PAX: remove macro guard in the struct definition

Macro guard in the struct definition will cause layout undetermined
if the macro definitions are inconsistent between compiling and use
of the header file.

Author: gfphoenix78

contrib/pax_storage/src/cpp/storage/micro_partition.h

@@ -204,12 +204,10 @@ class MicroPartitionReader {
 
     std::shared_ptr<PaxFilter> filter;
 
-#ifdef VEC_BUILD
-    TupleDesc tuple_desc = nullptr;
-#endif
-
     // should only reference
     std::shared_ptr<Bitmap8> visibility_bitmap = nullptr;
+
+    TupleDesc tuple_desc = nullptr;
   };
   MicroPartitionReader() = default;