Allow int keys when calling Redis methods

In 5bfc0f9, risky casting was invoked
as a way to show there is an issue here. However, it is not always
possible to use a string. For instance, there is no such thing as this
in PHP: ["1" => "whatever"]. If you try to create such an array, you
will obtain [1 => "whatever"] instead.

Ironically, this was copied in jetbrains/phpstorm, which is used in
PHPStan, which exhibited that false positive.

See JetBrains/phpstorm-stubs#1454

stubs/extensions/redis.phpstub

@@ -268,20 +268,20 @@ class Redis {
 
     public function ltrim(string $key, int $start , int $end): Redis|bool {}
 
-	/** @return false|list<false|string>|Redis */
+	/** @return false|list<false|int|string>|Redis */
     public function mget(array $keys) {}
 
     public function migrate(string $host, int $port, string $key, string $dst, int $timeout, bool $copy = false, bool $replace = false): bool {}
 
     public function move(string $key, int $index): bool {}
 
     /**
-     * @param array<string, string>
+     * @param array<int|string, string>
      */
     public function mset($key_values): Redis|bool {}
 
     /**
-     * @param array<string, string>
+     * @param array<int|string, string>
      */
     public function msetnx($key_values): Redis|bool {}