remove cirrus FreeBSD 12.2 build

.ci/export-cirrus-vars.sh

@@ -1,6 +1,6 @@
 #!/bin/sh -e
 
-# Export variables for later stages of the Azure pipeline
+# Export variables for later stages of the Cirrus pipeline
 # Values done in this manner will appear as environment variables
 # in later stages.
 

.cirrus.yml

@@ -99,12 +99,7 @@ linux_task:
 
 freebsd_task:
   matrix:
-    - name: FreeBSD 12.2
-      freebsd_instance:
-        image_family: freebsd-12-2
-        cpu: 8
-        memory: 8G
-    - name: FreeBSD 13
+    - name: Cirrus FreeBSD
       freebsd_instance:
         image_family: freebsd-13-0
         cpu: 8