Bump nth-check and optimize-css-assets-webpack-plugin (#882)

Bumps [nth-check](https://github.com/fb55/nth-check) and [optimize-css-assets-webpack-plugin](https://github.com/NMFR/optimize-css-assets-webpack-plugin). These dependencies needed to be updated together.

Updates `nth-check` from 1.0.2 to 2.1.1
- [Release notes](https://github.com/fb55/nth-check/releases)
- [Commits](fb55/nth-check@v1.0.2...v2.1.1)

Updates `optimize-css-assets-webpack-plugin` from 5.0.8 to 6.0.1
- [Release notes](https://github.com/NMFR/optimize-css-assets-webpack-plugin/releases)
- [Commits](NMFR/optimize-css-assets-webpack-plugin@v5.0.8...v6.0.1)

---
updated-dependencies:
- dependency-name: nth-check
  dependency-type: indirect
- dependency-name: optimize-css-assets-webpack-plugin
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]