Fix tree view if config contains " (#9250)

If you run DAG with `{"\"": ""}` configuration tree view will be broken:
```
tree:1 Uncaught SyntaxError: Unexpected string in JSON at position 806
    at JSON.parse (<anonymous>)
    at tree?dag_id=hightlight_test&num_runs=25:1190
```

JSON.parse is given incorrectly escaped json string.

airflow/www/templates/airflow/tree.html

@@ -136,7 +136,7 @@ function populate_taskinstance_properties(node) {
 
 var devicePixelRatio = window.devicePixelRatio || 1;
 // JSON.parse is faster for large payloads than an object literal (because the JSON grammer is simpler!)
-var data = JSON.parse('{{ data }}');
+var data = JSON.parse({{ data|tojson }});
 var barHeight = 20;
 var axisHeight = 40;
 var square_x = parseInt(500 * devicePixelRatio);