revert the revert crocodoc permissions change

This reverts the revert for CNVS-26051 as the data migration has
completed.

fixes CNVS-26154

test plan:
  * enable canvadocs (or crocodoc)
  * submit an assignment and annotate it as the teacher and student
  * re-submit the assignment
  * the student should still be able to view the *prior* submission's annotations

Change-Id: Id8dd00b1afffd0858e70ed315c2ebe00fe99201c
Reviewed-on: https://gerrit.instructure.com/69537
Reviewed-by: Cameron Matheson <cameron@instructure.com>
Tested-by: Jenkins
QA-Review: Jason Carter <jcarter@instructure.com>
Product-Review: Keith T. Garner <kgarner@instructure.com>

Author: ktgeek

app/models/crocodoc_document.rb

@@ -96,11 +96,7 @@ def permissions_for_user(user, whitelist = nil)
       opts[:filter] = user.crocodoc_id!
     end
 
-    submissions = attachment.attachment_associations.
-      where(:context_type => 'Submission').
-      preload(context: [:assignment]).
-      map(&:context)
-
+    submissions = self.submissions.preload(:assignment)
     if submissions.any? { |s| s.grants_right? user, :read_grade }
       opts[:filter] = 'all'
 

spec/models/crocodoc_document_spec.rb

@@ -116,8 +116,6 @@
     end
 
     it "returns permissions for older submission versions" do
-      pending
-
       submission2 = @assignment.submit_homework @submitter,
         submission_type: "online_upload",
         attachments: [crocodocable_attachment_model(context: @submitter)]