style(models): remove attr_accessible comment

Keep comments on model specifics.

app/models/charge.rb

@@ -4,8 +4,6 @@
 # A Charge represents a potential debit to a nonprofit's account on a credit card donation action.
 
 class Charge < ApplicationRecord
-  # TODO
-  # attr_accessible \
   # :amount,
   # :fee,
   # :stripe_charge_id,

app/models/comment.rb

@@ -2,9 +2,8 @@
 
 # License: AGPL-3.0-or-later WITH Web-Template-Output-Additional-Permission-3.0-or-later
 class Comment < ApplicationRecord
-  # TODO
-  # attr_accessible \
-  #   :host_id, :host_type, #parent: Event, Campaign, nil
+  # :host_id,
+  # :host_type, # parent: Event, Campaign, nil
   # :profile_id,
   # :body
 

app/models/coupon.rb

@@ -2,11 +2,11 @@
 
 # License: AGPL-3.0-or-later WITH Web-Template-Output-Additional-Permission-3.0-or-later
 class Coupon < ApplicationRecord
-  # attr_accessible \
   # :name,
   # :victim_np_id,
   # :paid, # boolean
-  # :nonprofit, :nonprofit_id
+  # :nonprofit,
+  # :nonprofit_id
 
   scope :unpaid, -> { where(paid: [nil, false]) }