Fix: pax object access hook assert false

When cbdb using `alter table` with PAX table, the `PaxObjectAccessHook` will be call.

Then sub_id will not be 0, because `attrnum` is not 0.

Author: jiaqizho

contrib/pax_storage/expected/ddl.out

@@ -65,7 +65,9 @@ drop table pax_test.t1;
 drop table pax_test.t2;
 -- alter column with options 
 create table pax_test.t3 (v1 numeric(100,1)) with(compresstype=zstd, compresslevel=1);
-NOTICE:  Table doesn't have 'DISTRIBUTED BY' clause -- Using column named 'v1' as the Cloudberry Database data distribution key for this table.
-HINT:  The 'DISTRIBUTED BY' clause determines the distribution of data. Make sure column(s) chosen are the optimal data distribution key to minimize skew.
 alter table pax_test.t3 alter column v1 type numeric;
 drop table pax_test.t3;
+-- add column with options
+create table pax_test.t4 (v1 text) with(compresstype=zstd, compresslevel=1);
+alter table pax_test.t4 add column v2 text;
+drop table pax_test.t4;

contrib/pax_storage/sql/ddl.sql

@@ -45,3 +45,7 @@ drop table pax_test.t2;
 create table pax_test.t3 (v1 numeric(100,1)) with(compresstype=zstd, compresslevel=1);
 alter table pax_test.t3 alter column v1 type numeric;
 drop table pax_test.t3;
+-- add column with options
+create table pax_test.t4 (v1 text) with(compresstype=zstd, compresslevel=1);
+alter table pax_test.t4 add column v2 text;
+drop table pax_test.t4;

contrib/pax_storage/src/cpp/access/pax_access_handle.cc

@@ -1108,8 +1108,6 @@ static void PaxObjectAccessHook(ObjectAccessType access, Oid class_id,
              rel->rd_options && RelationIsPAX(rel));
   if (!ok) goto out;
 
-  Assert(sub_id == 0);
-
   options = reinterpret_cast<paxc::PaxOptions *>(rel->rd_options);
   if (!options->partition_by()) {
     if (options->partition_ranges()) {