posts: remove rating, note, and status locks.

Remove the ability for users to lock ratings, note, and post statuses.

Historically the majority of locked posts were from 10+ years ago when
certain users habitually locked ratings and notes on every post they
touched for no reason. Nowadays most posts have been unlocked. Only a
handful of locked posts are left, none of which deserve to be locked.

The is_rating_locked, is_note_locked, and is_status_locked columns still
exist in the database, but aren't used.

app/models/post_approval.rb

@@ -8,10 +8,6 @@ class PostApproval < ApplicationRecord
   def validate_approval
     post.lock!
 
-    if post.is_status_locked?
-      errors.add(:post, "is locked and cannot be approved")
-    end
-
     if post.is_active?
       errors.add(:post, "is already active and cannot be approved")
     end