Post#is_approvable?: fix 'Approve' link appearing on approver's own uploads.

Fixes the 'Approve' link in the modqueue and in the quickmod bar being
shown as available on the approver's own flagged uploads, even though
they can't actually approve these posts.

app/models/post.rb

@@ -289,7 +289,7 @@ class Post < ApplicationRecord
 
   module ApprovalMethods
     def is_approvable?(user = CurrentUser.user)
-      !is_status_locked? && (is_pending? || is_flagged? || is_deleted?) && !approved_by?(user)
+      !is_status_locked? && (is_pending? || is_flagged? || is_deleted?) && uploader != user && !approved_by?(user)
     end
 
     def flag!(reason, options = {})