Citus relation stats: don't error out when shard_replication_factor > 1

[Sean Linsley]

citus_table_size() errors out if shard_replication_factor > 1 https://docs.citusdata.com/en/v10.2/admin_guide/table_management.html#table-size

To avoid dropping the stats for all tables, we should ignore this error. One way to do that would be to add a function in the pganalyze schema that calls the original Citus function wrapped in a try/catch block.