ci: remove test-bsd-unit workflow

This workflow doesn't provide much value. It mostly fails on temporary
errors regarding vagrant and doesn't provide a very useful signal that
the build is broken.

We perform cross-compilation and ensure `buildx` still compiles on
different bsd variants. That should be enough to make sure we don't
inadvertently break something.

Closes #3711.

Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>

.github/workflows/build.yml

@@ -250,73 +250,6 @@ jobs:
           name: test-reports-${{ env.TESTREPORTS_NAME }}
           path: ${{ env.TESTREPORTS_BASEDIR }}
 
-  test-bsd-unit:
-    runs-on: ubuntu-22.04
-    continue-on-error: true
-    strategy:
-      fail-fast: false
-      matrix:
-        os:
-          - freebsd
-          - netbsd
-          - openbsd
-    env:
-      # https://github.com/hashicorp/vagrant/issues/13652
-      VAGRANT_DISABLE_STRICT_DEPENDENCY_ENFORCEMENT: 1
-    steps:
-      -
-        name: Prepare
-        run: |
-          echo "VAGRANT_FILE=hack/Vagrantfile.${{ matrix.os }}" >> $GITHUB_ENV
-          
-          # Sets semver Go version to be able to download tarball during vagrant setup
-          goVersion=$(curl --silent "https://go.dev/dl/?mode=json&include=all" | jq -r '.[].files[].version' | uniq | sed -e 's/go//' | sort -V | grep $GO_VERSION | tail -1)
-          echo "GO_VERSION=$goVersion" >> $GITHUB_ENV
-      -
-        name: Checkout
-        uses: actions/checkout@v6
-      -
-        name: Cache Vagrant boxes
-        uses: actions/cache@v5
-        with:
-          path: ~/.vagrant.d/boxes
-          key: ${{ runner.os }}-vagrant-${{ matrix.os }}-${{ hashFiles(env.VAGRANT_FILE) }}
-          restore-keys: |
-            ${{ runner.os }}-vagrant-${{ matrix.os }}-
-      -
-        name: Install vagrant
-        run: |
-          set -x
-          wget -O - https://apt.releases.hashicorp.com/gpg | sudo gpg --dearmor -o /usr/share/keyrings/hashicorp-archive-keyring.gpg
-          echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/hashicorp-archive-keyring.gpg] https://apt.releases.hashicorp.com $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/hashicorp.list
-          sudo apt-get update
-          sudo apt-get install -y libvirt-dev libvirt-daemon libvirt-daemon-system vagrant vagrant-libvirt ruby-libvirt
-          sudo systemctl enable --now libvirtd
-          sudo chmod a+rw /var/run/libvirt/libvirt-sock
-          vagrant plugin install vagrant-libvirt
-          vagrant --version
-      -
-        name: Set up vagrant
-        run: |
-          ln -sf ${{ env.VAGRANT_FILE }} Vagrantfile
-          vagrant up --no-tty
-      -
-        name: Test
-        run: |
-          vagrant ssh -- "cd /vagrant; SKIP_INTEGRATION_TESTS=1 go test -mod=vendor -coverprofile=coverage.txt -covermode=atomic ${{ env.TESTFLAGS }} ./..."
-          vagrant ssh -c "sudo cat /vagrant/coverage.txt" > coverage.txt
-      -
-        name: Upload coverage
-        if: always()
-        uses: codecov/codecov-action@v5
-        with:
-          files: ./coverage.txt
-          env_vars: RUNNER_OS
-          flags: unit,${{ matrix.os }}
-          token: ${{ secrets.CODECOV_TOKEN }}
-        env:
-          RUNNER_OS: ${{ matrix.os }}
-
   govulncheck:
     runs-on: ubuntu-24.04
     permissions: