Simplify isort configuration using 'profile = black'

[jdufresne]

isort now has builtin support for black, use it.

Changelog-friendly one-liner: Simplify isort configuration using 'profile = black'

(I'm not sure this needs to be in the changelog, though.)

Contributor checklist

• Provided the tests for the changes. (N/A)
• Gave a clear one-line description in the PR (that the maintainers can add to CHANGELOG.md on release). (N/A)
• Assign the PR to an existing or new milestone for the target version (following Semantic Versioning).

[atugushev]

Thanks! 👍