Remove xdebug from CI (#586)

Author: Nyholm

.github/workflows/ci.yml

@@ -20,9 +20,9 @@ jobs:
         uses: shivammathur/[email protected]
         with:
           php-version: ${{ matrix.php }}
-          coverage: xdebug
+          coverage: none
           ini-values: xdebug.overload_var_dump=1
-          tools: prestissimo
+          tools: flex
 
       - name: Checkout code
         uses: actions/checkout@v2