Fix Client template

[franmomu]

#810 added generics to Client, that means that when using Client you should specify both parameters, getting this kind of message using static analysis tools:

Method App\My\Service::__construct() has parameter $redisClient with generic class Predis\Client but does not specify its types:
         TKey, TValue

Looking at what Client::getIterator() does:

predis/src/Client.php

Lines 523 to 539 in fbf2701

	public function getIterator()
	{
	$clients = array();
	$connection = $this->getConnection();
	if (!$connection instanceof Traversable) {
	return new \ArrayIterator(array(
	(string) $connection => new static($connection, $this->getOptions())
	));
	}
	foreach ($connection as $node) {
	$clients[(string) $node] = new static($node, $this->getOptions());
	}
	return new \ArrayIterator($clients);
	}

it returns an \ArrayIterator having as keys strings and as values instances of the class itself, so I think this class shouldn't be generic.

[tillkruss]

Are you running PHPStan? How do you feel about setting up basic level 1 or 2 testing for this repo?