FIX: use allowlist and blocklist terminology (#10209)

This is a PR of the renaming whitelist to allowlist and blacklist to the blocklist.

app/models/embeddable_host.rb

@@ -10,6 +10,9 @@ class EmbeddableHost < ActiveRecord::Base
     self.host.sub!(/\/.*$/, '')
   end
 
+  # TODO(2021-07-23): Remove
+  self.ignored_columns = ["path_whitelist"]
+
   def self.record_for_url(uri)
 
     if uri.is_a?(String)
@@ -31,9 +34,9 @@ class EmbeddableHost < ActiveRecord::Base
     path << "?" << uri.query if uri.query.present?
 
     where("lower(host) = ?", host).each do |eh|
-      return eh if eh.path_whitelist.blank?
+      return eh if eh.allowed_paths.blank?
 
-      path_regexp = Regexp.new(eh.path_whitelist)
+      path_regexp = Regexp.new(eh.allowed_paths)
       return eh if path_regexp.match(path) || path_regexp.match(UrlHelper.unencode(path))
     end
 
@@ -78,6 +81,6 @@ end
 #  category_id    :integer          not null
 #  created_at     :datetime         not null
 #  updated_at     :datetime         not null
-#  path_whitelist :string
+#  allowed_paths  :string
 #  class_name     :string
 #