fix(ec2): cannot set removal policy on VpcEndpointService

        ### Issue # (if applicable)

        Closes #30639.

        ### Reason for this change

        Cannot set removal policy on VpcEndpointService. defaultChild is not set.

        ### Description of changes

        Sets defaultChild of VpcEndpointService objects.

packages/aws-cdk-lib/aws-ec2/lib/vpc-endpoint-service.ts

@@ -114,6 +114,7 @@ export class VpcEndpointService extends Resource implements IVpcEndpointService
       acceptanceRequired: this.acceptanceRequired,
       contributorInsightsEnabled: this.contributorInsightsEnabled,
     });
+    this.node.defaultChild = this.endpointService;
 
     this.vpcEndpointServiceId = this.endpointService.ref;