Don't build partition info for local hypertables

So far, we have created fake partitioning info for hypertables if the
PostgreSQL setting 'enable_partitionwise_aggregate' is set. This causes
PostgreSQL to push down partial aggregations to the chunk level.
However, the PostgreSQL code has some drawbacks because the query is
replanned and optimizations like ChunkAppend are lost. Since timescale#5596 we
have implemented our own code to push down partial aggregations.
Therefore, we can ignore the PostgreSQL setting from now on.

src/planner/expand_hypertable.c

@@ -1381,10 +1381,8 @@ ts_plan_expand_hypertable_chunks(Hypertable *ht, PlannerInfo *root, RelOptInfo *
 
 	/* Adding partition info will make PostgreSQL consider the inheritance
 	 * children as part of a partitioned relation. This will enable
-	 * partitionwise aggregation. */
-	if ((enable_partitionwise_aggregate &&
-		 !has_partialize_function((Node *) root->parse->targetList, TS_DO_NOT_FIX_AGGSPLIT)) ||
-		hypertable_is_distributed(ht))
+	 * partitionwise aggregation for distributed queries. */
+	if (hypertable_is_distributed(ht))
 	{
 		build_hypertable_partition_info(ht, root, rel, list_length(inh_oids));
 	}