reverted:
--- b/core/lib/Drupal/Core/Plugin/DefaultLazyPluginCollection.php
+++ a/core/lib/Drupal/Core/Plugin/DefaultLazyPluginCollection.php
@@ -24,8 +24,6 @@
 class DefaultLazyPluginCollection extends LazyPluginCollection {
   use DependencySerializationTrait;
 
-  use DependencySerializationTrait;
-
   /**
    * The manager used to instantiate the plugins.
    *
reverted:
--- b/core/lib/Drupal/Core/Plugin/DefaultSingleLazyPluginCollection.php
+++ a/core/lib/Drupal/Core/Plugin/DefaultSingleLazyPluginCollection.php
@@ -24,8 +24,6 @@
 class DefaultSingleLazyPluginCollection extends LazyPluginCollection {
   use DependencySerializationTrait;
 
-  use DependencySerializationTrait;
-
   /**
    * The manager used to instantiate the plugins.
    *