[Refactor] Rename pointer_size_mapt -> type_size_mapt in unit tests

Author: NlightNFotis

unit/solvers/smt2_incremental/convert_expr_to_smt.cpp

@@ -58,7 +58,7 @@ struct expr_to_smt_conversion_test_environmentt
 
   smt_object_mapt object_map;
   smt_object_sizet object_size_function;
-  pointer_size_mapt pointer_sizes;
+  type_size_mapt pointer_sizes;
 
 private:
   // This is private to ensure the above make() function is used to make