Update voila requirement from ~=0.4.4 to ~=0.5.6

Updates the requirements on [voila](https://github.com/voila-dashboards/voila) to permit the latest version.
- [Release notes](https://github.com/voila-dashboards/voila/releases)
- [Changelog](https://github.com/voila-dashboards/voila/blob/main/CHANGELOG.md)
- [Commits](https://github.com/voila-dashboards/voila/compare/v0.4.4...@voila-dashboards/[email protected])

---
updated-dependencies:
- dependency-name: voila
  dependency-type: direct:production
...

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

requirements.txt

@@ -1,2 +1,2 @@
-voila~=0.4.4
+voila~=0.5.6
 jupyter-core~=5.3.1