Remove border from chromeless xblock

JIRA: https://openedx.atlassian.net/browse/MA-972

lms/djangoapps/courseware/testutils.py

@@ -30,6 +30,7 @@ class RenderXBlockTestMixin(object):
         '<footer id="footer-openedx"',
         '<div class="window-wrap"',
         '<div class="preview-menu"',
+        '<div class="container"'
     ]
 
     # DOM elements that appear in an xBlock,

lms/templates/courseware/courseware-chromeless.html

@@ -130,12 +130,10 @@ ${fragment.foot_html()}
 
 </%block>
 
-<div class="container">
-  <div class="course-wrapper">
-    <section class="course-content" id="course-content">
-      ${fragment.body_html()}
-    </section>
-  </div>
+<div class="course-wrapper">
+  <section class="course-content" id="course-content">
+    ${fragment.body_html()}
+  </section>
 </div>
 
 <nav class="nav-utilities ${"has-utility-calculator" if course.show_calculator else ""}" aria-label="${_('Course Utilities')}">