remove phpunit.yml, have no usecase yet

.github/workflows/phpunit.yml

@@ -1,51 +0,0 @@
-name: PHPUnit
-
-on:
-  pull_request:
-    branches: 
-      - develop
-
-jobs:
-  main:
-    name: Build and test
-
-    strategy:
-      matrix:
-        php-versions: ['7.2', '7.3', '7.4']
-
-    runs-on: ubuntu-latest
-
-    if: "!contains(github.event.head_commit.message, '[ci skip]')"
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2
-
-      - name: Setup PHP, with composer and extensions
-        uses: shivammathur/setup-php@master
-        with:
-          php-version: ${{ matrix.php-versions }}
-          tools: composer, pecl, phpunit
-          extensions: intl, json, mbstring, mysqlnd, xdebug, xml, sqlite3
-          coverage: xdebug
-
-      - name: Get composer cache directory
-        id: composer-cache
-        run: echo "::set-output name=dir::$(composer config cache-files-dir)"
-
-      - name: Cache composer dependencies
-        uses: actions/cache@v1
-        with:
-          path: ${{ steps.composer-cache.outputs.dir }}
-          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.json') }}
-          restore-keys: ${{ runner.os }}-composer-
-
-      - name: Install dependencies
-        run: composer install --no-progress --no-suggest --no-interaction --prefer-dist --optimize-autoloader
-        # To prevent rate limiting you may need to supply an OAuth token in Settings > Secrets
-        # env:
-          # https://getcomposer.org/doc/articles/troubleshooting.md#api-rate-limit-and-oauth-tokens
-          # COMPOSER_AUTH: ${{ secrets.COMPOSER_AUTH }}
-
-      - name: Test with phpunit
-        run: vendor/bin/phpunit --coverage-text