Bump x509-limbo and/or wycheproof in CI (#12998)

Co-authored-by: pyca-boringbot[bot] <pyca-boringbot[bot][email protected]>

Author: pyca-boringbot[bot]

.github/actions/fetch-vectors/action.yml

@@ -16,5 +16,5 @@ runs:
       with:
         repository: "C2SP/x509-limbo"
         path: "x509-limbo"
-        # Latest commit on the x509-limbo main branch, as of May 21, 2025.
-        ref: "72afb4cc77a1a663e5981e8261a56b93fb05f441" # x509-limbo-ref
+        # Latest commit on the x509-limbo main branch, as of May 28, 2025.
+        ref: "8cfd8af990a6d744e0cd97ce66bb5f63b907aa6e" # x509-limbo-ref