PHPStan fixes

core/modules/field/field.install

@@ -15,7 +15,7 @@ function field_update_last_removed(): int {
 /**
  * Adds default config for Show add more button for multivalued fields.
  */
-function field_update_9001() {
+function field_update_9001(): void {
   // Get all the fields which are multivalued but not unlimited cardinality.
   $query = \Drupal::entityQuery('field_storage_config')
     ->condition('cardinality', 1, '>')