Fix credentials parsing for redshift

[romanoff]

Fix CREDENTIALS keyword parsing for redshift

Sample query:

COPY table1
FROM 's3://my-bucket/my-file.csv'
CREDENTIALS 'aws_access_key_id=AKIAEXAMPLE;aws_secret_access_key=SECRETEXAMPLE'
CSV;

Spec: https://docs.aws.amazon.com/redshift/latest/dg/copy-parameters-authorization.html?utm_source=chatgpt.com

[iffyio]

LGTM! Thanks @romanoff!