ci(vagrant): remove testing for unsupported OSes

.github/workflows/kitchen.vagrant.yml

@@ -1,37 +0,0 @@
-# -*- coding: utf-8 -*-
-# vim: ft=yaml
----
-name: 'Kitchen Vagrant (FreeBSD & OpenBSD)'
-'on': ['push', 'pull_request']
-
-env:
-  KITCHEN_LOCAL_YAML: 'kitchen.vagrant.yml'
-
-jobs:
-  test:
-    runs-on: 'macos-10.15'
-    strategy:
-      fail-fast: false
-      matrix:
-        instance:
-          - default-freebsd-130-master-py3
-          - default-freebsd-123-master-py3
-          # - default-freebsd-130-3004-0-py3
-          # - default-freebsd-123-3004-0-py3
-          - default-openbsd-70-3003-3-py3
-    steps:
-      - name: 'Check out code'
-        uses: 'actions/checkout@v2'
-      - name: 'Set up Bundler cache'
-        uses: 'actions/cache@v1'
-        with:
-          path: 'vendor/bundle'
-          key: "${{ runner.os }}-gems-${{ hashFiles('**/Gemfile.lock') }}"
-          restore-keys: "${{ runner.os }}-gems-"
-      - name: 'Run Bundler'
-        run: |
-          ruby --version
-          bundle config path vendor/bundle
-          bundle install --jobs 4 --retry 3
-      - name: 'Run Test Kitchen'
-        run: 'bundle exec kitchen verify ${{ matrix.instance }}'