build(deps): bump github.com/open-policy-agent/opa from 1.6.0 to 1.8.0

Bumps [github.com/open-policy-agent/opa](https://github.com/open-policy-agent/opa) from 1.6.0 to 1.8.0.
- [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/v1.6.0...v1.8.0)

---
updated-dependencies:
- dependency-name: github.com/open-policy-agent/opa
  dependency-version: 1.8.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

vendor/github.com/tchap/go-patricia/v2/patricia/patricia.go

@@ -465,7 +465,7 @@ func (trie *Trie) compact() *Trie {
 	// If any item is set, we cannot compact since we want to retain
 	// the ability to do searching by key. This makes compaction less usable,
 	// but that simply cannot be avoided.
-	if trie.item != nil || child.item != nil {
+	if child == nil || trie.item != nil || child.item != nil {
 		return trie
 	}