Styling changes:

- move `usa-accordion` class to wrap all accordion elements
- remove background color form `accordion` class and move it to atat
specific class `accordion__header`
- create class names for styling elements instead of relying on element
type

templates/task_orders/index.html

@@ -14,7 +14,7 @@
 
 {% macro TaskOrderList(task_orders, status) %}
   {% set status = "All Task Orders" %}
-  <div class="accordion">
+  <div class="accordion usa-accordion">
     {% call Accordion(title=status, id=status, heading_tag="h4") %}
       {% for task_order in task_orders %}
         <div class="accordion__content--list-item">