Fix incorrect return type for wpcf7_swv_create_rule() mentioned in PhpDoc

[koloml]

Function wpcf7_swv_create_rule mentions Rule class without a namespace. This is causing IDE to show type warnings when adding rules to the WPCF7_SWV_Schema object:

class Example
{
    public function add_rules( \WPCF7_SWV_Schema $schema ): void
    {
        $schema->add_rule(
            wpcf7_swv_create_rule( 'required', [
                'field' => 'example',
                'error' => wpcf7_get_message( 'invalid_required' )
            ] )
        );
    }
}

Here is a screenshot of this warning from PhpStorm:

After adding the namespace to the returned type, warning goes away.