Revert "Issue #2694391 by chx, benjy, catch, dawehner: Separate cache bin for migrations"

This reverts commit 74268797.

core/modules/migrate/migrate.services.yml

@@ -17,12 +17,6 @@ services:
   plugin.manager.migrate.id_map:
     class: Drupal\migrate\Plugin\MigratePluginManager
     arguments: [id_map, '@container.namespaces', '@cache.discovery', '@module_handler']
-  cache.discovery_migration:
-    class: Drupal\Core\Cache\CacheBackendInterface
-    tags:
-      - { name: cache.bin, default_backend: cache.backend.memory }
-    factory: cache_factory:get
-    arguments: [discovery_migration]
   plugin.manager.migration:
     class: Drupal\migrate\Plugin\MigrationPluginManager
-    arguments: ['@module_handler', '@cache.discovery_migration', '@language_manager']
+    arguments: ['@module_handler', '@cache.discovery', '@language_manager']