clean install

web/core/modules/migrate/migrate.post_update.php

@@ -0,0 +1,15 @@
+<?php
+
+/**
+ * @file
+ * Post update functions for migrate.
+ */
+
+/**
+ * Implements hook_removed_post_updates().
+ */
+function migrate_removed_post_updates() {
+  return [
+    'migrate_post_update_clear_migrate_source_count_cache' => '10.0.0',
+  ];
+}