TransactionalSMSApi constructor nullable parameters (PHP 8.4)

[sigkoro]

The constructor of TransactionalSMSApi should be fixed the same way you fixed TransactionalEmailApi to be compatible with php 8.4.

public function __construct(
        ?ClientInterface $client = null,
        ?Configuration $config = null,
        ?HeaderSelector $selector = null
    ) {
        $this->client = $client ?: new Client();
        $this->config = $config ?: new Configuration();
        $this->headerSelector = $selector ?: new HeaderSelector();
    }

[sigkoro]

@sowmyahora2001 could you consider this issue in the next release please ? btw you could do the same with all APIs i think.