Bump postcss-attribute-case-insensitive from 6.0.2 to 6.0.3

Bumps [postcss-attribute-case-insensitive](https://github.com/csstools/postcss-plugins/tree/HEAD/plugins/postcss-attribute-case-insensitive) from 6.0.2 to 6.0.3.
- [Changelog](https://github.com/csstools/postcss-plugins/blob/main/plugins/postcss-attribute-case-insensitive/CHANGELOG.md)
- [Commits](https://github.com/csstools/postcss-plugins/commits/HEAD/plugins/postcss-attribute-case-insensitive)

---
updated-dependencies:
- dependency-name: postcss-attribute-case-insensitive
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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