test: remove Cirrus CI FreeBSD job

This has been removed from the master branch, and always seems to fail
at the installing packages phase. i.e:
```bash
pkg install -y autoconf automake boost-libs git gmake libevent libtool pkgconf python3 ccache
Updating FreeBSD repository catalogue...
Fetching meta.txz: . done
pkg: repository meta /var/db/pkg/FreeBSD.meta has wrong version 2
repository FreeBSD has no meta file, using default settings
Fetching packagesite.txz: .......... done
pkg: repository meta /var/db/pkg/FreeBSD.meta has wrong version 2
pkg: Repository FreeBSD load error: meta cannot be loaded No error: 0
Unable to open created repository FreeBSD
Unable to update repository FreeBSD
Error updating repositories!

Exit status: 3
```

.cirrus.yml

@@ -1,33 +1,3 @@
-task:
-  name: "FreeBsd 12.0 amd64  [GOAL: install]  [no depends, only system libs]"
-  freebsd_instance:
-    image: freebsd-12-0-release-amd64
-    cpu: 8
-    memory: 8G
-  timeout_in: 60m
-  env:
-    MAKEJOBS: "-j9"
-    CONFIGURE_OPTS: "--disable-dependency-tracking"
-    GOAL: "install"
-    TEST_RUNNER_PORT_MIN: "14000"  # Must be larger than 12321, which is used for the http cache. See https://cirrus-ci.org/guide/writing-tasks/#http-cache
-    CCACHE_SIZE: "200M"
-    CCACHE_COMPRESS: 1
-    CCACHE_DIR: "/tmp/ccache_dir"
-  ccache_cache:
-    folder: "/tmp/ccache_dir"
-  install_script:
-    - pkg install -y autoconf automake boost-libs git gmake libevent libtool pkgconf python3 ccache
-    - ./contrib/install_db4.sh $(pwd)
-    - ccache --max-size=${CCACHE_SIZE}
-  configure_script:
-    - ./autogen.sh
-    - ./configure ${CONFIGURE_OPTS} BDB_LIBS="-L$(pwd)/db4/lib -ldb_cxx-4.8" BDB_CFLAGS="-I$(pwd)/db4/include" || ( cat config.log && false)
-  make_script:
-    - gmake ${MAKEJOBS} ${GOAL} || ( echo "Build failure. Verbose build follows." && gmake ${GOAL} V=1 ; false )
-  check_script:
-    - gmake check ${MAKEJOBS} VERBOSE=1
-  functional_test_script:
-    - ./test/functional/test_runner.py --jobs 9 --ci --extended --exclude feature_dbcrash --combinedlogslen=1000 --quiet --failfast
 task:
   name: "x86_64 Linux  [GOAL: install]  [bionic]  [Using ./ci/ system]"
   container: