Update changie config to match other repos

[jtcohen6]

The .changie yaml config in dbt-adapters (and dbt-postgres):

• https://github.com/dbt-labs/dbt-adapters/blob/main/.changie.yaml
• https://github.com/dbt-labs/dbt-postgres/blob/main/.changie.yaml

Doesn't match the config in other repos, e.g.

• https://github.com/dbt-labs/dbt-core/blob/main/.changie.yaml
• https://github.com/dbt-labs/dbt-snowflake/blob/main/.changie.yaml

The changelog is missing nice things we have in other repositories, such as PR links and contributors.

This is separate (and simpler) work from the desire to produce separate changelogs for dbt-adapters and dbt-tests-adapter:

• [Tech Debt] Establish a separate changelog process for dbt-tests-adapter #206