Bump dagster from 1.6.4 to 1.6.8 (#168)

Bumps [dagster](https://github.com/dagster-io/dagster) from 1.6.4 to 1.6.8.
- [Release notes](https://github.com/dagster-io/dagster/releases)
- [Changelog](https://github.com/dagster-io/dagster/blob/master/CHANGES.md)
- [Commits](dagster-io/dagster@1.6.4...1.6.8)

---
updated-dependencies:
- dependency-name: dagster
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

pyproject.toml

@@ -56,7 +56,7 @@ test = [
   "pendulum >= 2.1.2"
 ]
 dagster = [
-  "dagster == 1.6.4"
+  "dagster == 1.6.8"
 ]
 cloud = [
   "msgpack == 1.0.8"