posts: clean up delete! method.

* Remove unused `ban` and `without_mod_action` options.

* Don't try to set the `is_banned` flag during deletion.

* Don't create modactions for automatic "unapproved in 3 days"
  deletions, only to delete them after the fact.

app/models/post_flag.rb

@@ -13,7 +13,7 @@ class PostFlag < ApplicationRecord
   validates :reason, presence: true, length: { in: 1..140 }
   validate :validate_creator_is_not_limited, on: :create
   validate :validate_post
-  validates_uniqueness_of :creator_id, :scope => :post_id, :on => :create, :unless => :is_deletion, :message => "have already flagged this post"
+  validates_uniqueness_of :creator_id, scope: :post_id, on: :create, unless: :is_deletion, message: "have already flagged this post"
   before_save :update_post
   attr_accessor :is_deletion