Update scikit-build requirement in /docker/main

Updates the requirements on [scikit-build](https://github.com/scikit-build/scikit-build) to permit the latest version.
- [Release notes](https://github.com/scikit-build/scikit-build/releases)
- [Changelog](https://github.com/scikit-build/scikit-build/blob/main/CHANGES.md)
- [Commits](https://github.com/scikit-build/scikit-build/compare/0.18.0...0.19.1)

---
updated-dependencies:
- dependency-name: scikit-build
  dependency-version: 0.19.1
  dependency-type: direct:production
...

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

docker/main/requirements.txt

@@ -1 +1 @@
-scikit-build == 0.18.*
+scikit-build == 0.19.*