remove spurious </ul> after direct share menu items

test plan:
 - have an LTI tool with assignment_menu placement installed
 - enable the direct share feature flag
 - on the assignments index page, the LTI tool's placement
   should appear after the "Copy To" and "Send To" items
   inside the menu (and should _not_ be visible _outside_
   the menu)

flag: direct_share
fixes LA-351

Change-Id: Ie0261aa2e63bd7fc7007c698a73bd744c623bff8
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/220290
Reviewed-by: Mysti Lilla <mysti@instructure.com>
Reviewed-by: Carl Kibler <ckibler@instructure.com>
QA-Review: Anju Reddy <areddy@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Tested-by: Jenkins
Product-Review: Jeremy Stanley <jeremy@instructure.com>

app/views/jst/assignments/AssignmentListItem.handlebars

@@ -226,14 +226,12 @@
                     aria-label="{{#t}}Send Assignment {{name}} to another user{{/t}}"
                 >{{#t}}Send To...{{/t}}</a>
               </li>
-                <li>
-                  <a
-                    class="copy_assignment_to icon-duplicate"
-                    id="assignment_{{id}}_settings_copy_to"
-                    aria-label="{{#t}}Copy Assignment {{name}} to another course{{/t}}"
-                  >{{#t}}Copy To...{{/t}}</a>
-                </li>
-                </ul>
+              <li>
+                <a
+                  class="copy_assignment_to icon-duplicate"
+                  id="assignment_{{id}}_settings_copy_to"
+                  aria-label="{{#t}}Copy Assignment {{name}} to another course{{/t}}"
+                >{{#t}}Copy To...{{/t}}</a>
               </li>
             {{/if}}
             {{>ExternalTools/external_tools_menu menu_tools}}