Omit chain from DuckDB S3 secret

Why these changes are being introduced:

It sounds like the best option for ECS tasks is using 'instance'
as the provider chain type, where for local dev and/or lambdas
it might be 'sso' or 'env'.  Not having 'instance' appears to cause
failures in the ECS task.

How this addresses that need:

By omitting the 'chain' option entirely from DuckDB secret creation
we allow the default provider chain to take effect.  Given our fairly
normal usage of DuckDB and S3, this is probably the best approach.

Side effects of this change:
* DuckDB to S3 connections work in ECS

Relevant ticket(s):
* https://mitlibraries.atlassian.net/browse/TIMX-540

Author: ghukill

timdex_dataset_api/metadata.py

@@ -194,7 +194,6 @@ def _configure_duckdb_s3_secret(
                 create or replace secret aws_s3_secret (
                     type s3,
                     provider credential_chain,
-                    chain 'sso;env;config',
                     refresh true
                     {scope_str}
                 );