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/sergi/go-diff/diffmatchpatch/stringutil.go

@@ -93,14 +93,14 @@ func runesIndex(r1, r2 []rune) int {
 	return -1
 }
 
-func intArrayToString(ns []uint32) string {
+func intArrayToString(ns []index) string {
 	if len(ns) == 0 {
 		return ""
 	}
 
 	b := []rune{}
 	for _, n := range ns {
-		b = append(b, intToRune(n))
+		b = append(b, intToRune(uint32(n)))
 	}
 	return string(b)
 }