Bump flake8-builtins from 1.5.3 to 2.1.0

Bumps [flake8-builtins](https://github.com/gforcada/flake8-builtins) from 1.5.3 to 2.1.0.
- [Release notes](https://github.com/gforcada/flake8-builtins/releases)
- [Changelog](https://github.com/gforcada/flake8-builtins/blob/master/CHANGES.rst)
- [Commits](gforcada/flake8-builtins@1.5.3...2.1.0)

---
updated-dependencies:
- dependency-name: flake8-builtins
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]