build(deps): bump github.com/distribution/reference from 0.5.0 to 0.6.0

Bumps [github.com/distribution/reference](https://github.com/distribution/reference) from 0.5.0 to 0.6.0.
- [Release notes](https://github.com/distribution/reference/releases)
- [Commits](https://github.com/distribution/reference/compare/v0.5.0...v0.6.0)

---
updated-dependencies:
- dependency-name: github.com/distribution/reference
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

go.mod

@@ -28,7 +28,7 @@ require (
 	github.com/containernetworking/plugins v1.4.1
 	github.com/coreos/go-systemd/v22 v22.5.0
 	github.com/davecgh/go-spew v1.1.1
-	github.com/distribution/reference v0.5.0
+	github.com/distribution/reference v0.6.0
 	github.com/docker/go-events v0.0.0-20190806004212-e31b211e4f1c
 	github.com/docker/go-metrics v0.0.1
 	github.com/docker/go-units v0.5.0