ci: Drop ubuntu-16.04 (#606)

.github/workflows/test.yml

@@ -18,7 +18,6 @@ jobs:
         os:
           - 'ubuntu-20.04'
           - 'ubuntu-18.04'
-          - 'ubuntu-16.04'
           - 'macos-latest'
           - 'windows-latest'
     steps:
@@ -114,24 +113,6 @@ jobs:
           # commit_message: ${{ github.event.head_commit.message }}
           cname: 'actions-gh-pages.peaceiris.com'
 
-      - name: Deploy
-        if: |
-          startsWith(matrix.os, 'ubuntu-16.04') &&
-          github.ref == 'refs/heads/main' && github.event.repository.fork == false
-        uses: ./
-        with:
-          deploy_key: ${{ secrets.ACTIONS_DEPLOY_KEY }}
-          # github_token: ${{ secrets.GITHUB_TOKEN }}
-          publish_branch: gh-pages-ubuntu-16.04
-          publish_dir: ./test_projects/mdbook/book
-          # external_repository: ''
-          allow_empty_commit: true
-          keep_files: true
-          force_orphan: true
-          user_name: 'github-actions[bot]'
-          user_email: 'github-actions[bot]@users.noreply.github.com'
-          full_commit_message: ${{ github.event.head_commit.message }}
-
       - name: Deploy
         if: |
           startsWith(matrix.os, 'macos') &&