build(deps): bump github.com/open-policy-agent/opa from 1.5.0 to 1.5.1

Bumps [github.com/open-policy-agent/opa](https://github.com/open-policy-agent/opa) from 1.5.0 to 1.5.1.
- [Release notes](https://github.com/open-policy-agent/opa/releases)
- [Changelog](https://github.com/open-policy-agent/opa/blob/main/CHANGELOG.md)
- [Commits](https://github.com/open-policy-agent/opa/compare/v1.5.0...v1.5.1)

---
updated-dependencies:
- dependency-name: github.com/open-policy-agent/opa
  dependency-version: 1.5.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

go.mod

@@ -62,7 +62,7 @@ require (
 	github.com/onsi/ginkgo v1.16.5
 	github.com/onsi/ginkgo/v2 v2.23.4
 	github.com/onsi/gomega v1.37.0
-	github.com/open-policy-agent/opa v1.5.0
+	github.com/open-policy-agent/opa v1.5.1
 	github.com/opencloud-eu/libre-graph-api-go v1.0.8-0.20250603072916-fa601fb14450
 	github.com/opencloud-eu/reva/v2 v2.33.1-0.20250603070030-797b412f62db
 	github.com/orcaman/concurrent-map v1.0.0