aliases/implications: remove 'error' state.

Remove the error status from aliases and implications. Aliases and
implications normally shouldn't fail because they're validated
beforehand. If they do, just let the delayed job itself record the
failure.

Also disable the delayed job from retrying if the alias/implication
somehow fails.

app/models/tag_alias.rb

@@ -12,9 +12,6 @@ class TagAlias < TagRelationship
 
   def process!
     TagMover.new(antecedent_name, consequent_name, user: User.system).move!
-  rescue Exception => e
-    update!(status: "error: #{e}")
-    DanbooruLogger.log(e, tag_alias_id: id, antecedent_name: antecedent_name, consequent_name: consequent_name)
   end
 
   def absence_of_transitive_relation

app/models/tag_implication.rb

@@ -113,9 +113,6 @@ class TagImplication < TagRelationship
       CurrentUser.scoped(User.system) do
         update_posts
       end
-    rescue Exception => e
-      update(status: "error: #{e}")
-      DanbooruLogger.log(e, tag_implication_id: id, antecedent_name: antecedent_name, consequent_name: consequent_name)
     end
 
     def create_mod_action

app/models/tag_relationship.rb

@@ -20,7 +20,7 @@ class TagRelationship < ApplicationRecord
   scope :retired, -> {where(status: "retired")}
 
   before_validation :normalize_names
-  validates_format_of :status, :with => /\A(active|deleted|retired|error: .*)\Z/
+  validates :status, inclusion: { in: %w[active deleted retired] }
   validates_presence_of :antecedent_name, :consequent_name
   validates :approver, presence: { message: "must exist" }, if: -> { approver_id.present? }
   validates :forum_topic, presence: { message: "must exist" }, if: -> { forum_topic_id.present? }
@@ -47,10 +47,6 @@ class TagRelationship < ApplicationRecord
     status == "active"
   end
 
-  def is_errored?
-    status =~ /\Aerror:/
-  end
-
   def reject!
     update!(status: "deleted")
   end