Fix faulty permission handling for choose home page button

fixes: LS-2830
flag=none

test plan:

- Disable the 'Course Content - add / edit / delete'
permission for a role based on course designer

- Enroll a user with this role in a course

- As the user, see that you can no longer choose
the home page

Change-Id: Ia0c7b62aa96bdb5370bcd02551e7e88633639967
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/279759
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Nate Armstrong <narmstrong@instructure.com>
QA-Review: Nate Armstrong <narmstrong@instructure.com>
Product-Review: Luis Oliveira <luis.oliveira@instructure.com>

app/views/courses/_course_show_secondary.html.erb

@@ -20,7 +20,7 @@
   <% if @can_manage || @can_create_announcements || @course_home_view != 'feed' || @course_home_sub_navigation_tools.present? %>
   <div class="course-options">
     <%= external_tools_menu_items(@course_home_sub_navigation_tools, {link_class: "btn button-sidebar-wide course-home-sub-navigation-lti", settings_key: :course_home_sub_navigation}) %>
-    <% if @can_manage && !@context.elementary_homeroom_course? %>
+    <% if can_do(@context, @current_user, :manage_content) && !@context.elementary_homeroom_course? %>
     <div id="choose_home_page"></div>
     <div id="choose_home_page_not_modules"></div>
     <% end %>