Correct Guzzle argument to control SSL verification.

Closes #3525647

src/Plugin/OpenSearch/Connector/StandardConnector.php

@@ -161,7 +161,7 @@ class StandardConnector extends PluginBase implements OpenSearchConnectorInterfa
   protected function getClientOptions(): array {
     return [
       'base_uri' => $this->configuration['url'],
-      'verify_ssl' => $this->configuration['ssl_verification'],
+      'verify' => $this->configuration['ssl_verification'],
     ];
   }