small manage_assignments cleanup

Change-Id: Ie8bc261ef5bf5f27f5450e355d077dbad679dc5d
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/271084
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
QA-Review: Simon Williams <simon@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>

app/controllers/assignments_api_controller.rb

@@ -799,7 +799,7 @@ class AssignmentsApiController < ApplicationController
         scope = SortsAssignments.bucket_filter(scope, params[:bucket], session, user, @current_user, @context, submissions_for_user)
       end
 
-      scope = scope.where(post_to_sis: value_to_boolean(params[:post_to_sis])) if params[:post_to_sis] && authorized_action(@context, user, :manage_assignments)
+      scope = scope.where(post_to_sis: value_to_boolean(params[:post_to_sis])) if params[:post_to_sis]
 
       if params[:assignment_ids]
         if params[:assignment_ids].length > Api.max_per_page

app/models/assignment.rb

@@ -1725,7 +1725,7 @@ class Assignment < ActiveRecord::Base
     can :manage_files_delete
 
     given { |user, session| self.context.grants_right?(user, session, :manage_assignments) }
-    can :create and can :read and can :attach_submission_comment_files
+    can :create and can :read
 
     given { |user, session| self.user_can_update?(user, session) }
     can :update