Bring back dbt 1.8

[amishas157]

PR Checklist

PR Structure

• This PR has reasonably narrow scope (if not, break it down into smaller PRs).
• This PR avoids mixing refactoring changes with feature changes (split into two PRs
  otherwise).
• This PR's title starts with the jira ticket associated with the PR.

Thoroughness

• This PR adds tests for the most critical parts of the new functionality or fixes.
• I've updated the README with the added features, breaking changes, new instructions on how to use the repository.

What

Ref: #475

This PR fixes error shown up from dbt upgrade.

Why

Noted inline

Known limitations

[TODO or N/A]

[amishas157]

This variable is used in following

stellar-etl-airflow/dags/stellar_etl_airflow/build_dbt_task.py

Line 16 in 5a2bed1

dbt_dataset = "{{ var.value.dbt_dataset_for_test }}"

In previous versions of dbt <=1.3, it was okay to pass empty string in dbt_dataset but not anymore. Also this value does not mean anything. It is just a required variable