Cirrus-CI: Bump to FreeBSD 13.5 image

It is currently the oldest supported FreeBSD 13 release.

Sponsored by:	The FreeBSD Foundation

.cirrus.yml

@@ -4,7 +4,7 @@ compute_engine_instance:
   # gcloud compute images list --project freebsd-org-cloud-dev --no-standard-images
   platform: freebsd
   image_project: freebsd-org-cloud-dev
-  image: freebsd-13-4-release-amd64
+  image: freebsd-13-5-release-amd64
   cpu: 8
   memory: 8G
   disk: 40