Bump x509-limbo and/or wycheproof in CI (pyca#11495)

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 Aug 20, 2024.
-        ref: "9cc4d0526d901b6121a1e975e6e21b273ddde8fd" # x509-limbo-ref
+        # Latest commit on the x509-limbo main branch, as of Aug 27, 2024.
+        ref: "6b9a21829ab580c2893ff0e6fd310fa94accd6c3" # x509-limbo-ref