Update openpolicyagent/opa Docker tag to v1.8.0 (#2746)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

dependencies.Dockerfile

@@ -6,7 +6,7 @@
 FROM otel/weaver:v0.17.1@sha256:32523b5e44fb44418786347e9f7dde187d8797adb6d57a2ee99c245346c3cdfe AS weaver
 
 # OPA is used to test policies enforced by weaver.
-FROM openpolicyagent/opa:1.7.1@sha256:e14c54bddfd680d051db44eab44d4b7ec96609a60d4359e04273b9a1457ce3c4 AS opa
+FROM openpolicyagent/opa:1.8.0@sha256:0917dda453560b65798d3c78caed0376c4db0708f1e4df5724058a5dfd412948 AS opa
 
 # Lychee is used for checking links in documentation.
 FROM lycheeverse/lychee:sha-2aa22f8@sha256:2e3786630482c41f9f2dd081e06d7da1c36d66996e8cf6573409b8bc418d48c4 AS lychee