[Feature] Update documentation of integration tests as it relates to CircleCI / GHA

### Is this your first time submitting a feature request?

- [X] I have read the [expectations for open source contributors](https://docs.getdbt.com/docs/contributing/oss-expectations)
- [X] I have searched the existing issues, and I could not find an existing issue for this feature
- [X] I am requesting a straightforward extension of existing dbt-spark functionality, rather than a Big Idea better suited to a discussion

### Describe the feature

Update this documentation to reflect the switch from CircleCI to GitHub Actions in https://github.com/dbt-labs/dbt-spark/pull/923:

https://github.com/dbt-labs/dbt-spark/blob/212442322b509eb34deee2ac000c85c1e4daba73/.github/workflows/release.yml#L89-L94

### Describe alternatives you've considered

_No response_

### Who will this benefit?

Up-to-date documentation. I found this instance when doing a code search for "CircleCI".

### Are you interested in contributing this feature?

_No response_

### Anything else?

_No response_