Update to Drupal 8.1.0. For more information, see https://www.drupal.org/drupal-8.1.0-release-notes

core/modules/field/migration_templates/d6_field.yml

@@ -2,9 +2,8 @@ id: d6_field
 label: Field configuration
 migration_tags:
   - Drupal 6
-builder:
-  plugin: d6_cck_migration
-  cck_plugin_method: processField
+class: Drupal\migrate_drupal\Plugin\migrate\CckMigration
+cck_plugin_method: processField
 source:
   plugin: d6_field
   constants:

core/modules/field/migration_templates/d6_field_formatter_settings.yml

@@ -2,9 +2,8 @@ id: d6_field_formatter_settings
 label: Field formatter configuration
 migration_tags:
   - Drupal 6
-builder:
-  plugin: d6_cck_migration
-  cck_plugin_method: processFieldFormatter
+class: Drupal\migrate_drupal\Plugin\migrate\CckMigration
+cck_plugin_method: processFieldFormatter
 source:
   plugin: d6_field_instance_per_view_mode
   constants:

core/modules/field/migration_templates/d6_field_instance.yml

@@ -2,9 +2,8 @@ id: d6_field_instance
 label: Field instance configuration
 migration_tags:
   - Drupal 6
-builder:
-  plugin: d6_cck_migration
-  cck_plugin_method: processFieldInstance
+class: Drupal\migrate_drupal\Plugin\migrate\CckMigration
+cck_plugin_method: processFieldInstance
 source:
   plugin: d6_field_instance
   constants:

core/modules/field/migration_templates/d6_field_instance_widget_settings.yml

@@ -2,9 +2,8 @@ id: d6_field_instance_widget_settings
 label: Field instance widget configuration
 migration_tags:
   - Drupal 6
-builder:
-  plugin: d6_cck_migration
-  cck_plugin_method: processFieldWidget
+class: Drupal\migrate_drupal\Plugin\migrate\CckMigration
+cck_plugin_method: processFieldWidget
 source:
   plugin: d6_field_instance_per_form_display
   constants: