FreeBSD CI: switch to the latest 12.1-RELEASE

.cirrus.yml

@@ -1,6 +1,6 @@
 FreeBSD_task:
   freebsd_instance:
-    image: freebsd-12-0-release-amd64
+    image: freebsd-12-1-release-amd64
   env:
     ASSUME_ALWAYS_YES: TRUE # required for unattanded "pkg" invocation
   install_script: