Add subversion installation to PHPUnit workflow

Added a step to install subversion in the GitHub Actions PHPUnit workflow. This ensures that subversion is available before installing the WordPress test suite, which may require it.

Author: pfefferle

.github/workflows/phpunit.yml

@@ -43,6 +43,9 @@ jobs:
       - name: Install dependencies
         run: composer install --prefer-dist --no-progress
 
+      - name: Install subversion
+        run: sudo apt-get update && sudo apt-get install -y subversion
+
       - name: Install WordPress test suite
         run: |
           bash bin/install-wp-tests.sh wordpress_test root root 127.0.0.1 ${{ matrix.wp-version }}