Refactor `OC\Server::getGetRedisFactory`

Signed-off-by: Andrew Summers <18727110+summersab@users.noreply.github.com>

lib/private/Memcache/Redis.php

@@ -70,7 +70,7 @@ class Redis extends Cache implements IMemcacheTTL {
 	 */
 	public function getCache() {
 		if (is_null(self::$cache)) {
-			self::$cache = \OC::$server->getGetRedisFactory()->getInstance();
+			self::$cache = \OC::$server->get('RedisFactory')->getInstance();
 		}
 		return self::$cache;
 	}
@@ -209,7 +209,7 @@ class Redis extends Cache implements IMemcacheTTL {
 	}
 
 	public static function isAvailable(): bool {
-		return \OC::$server->getGetRedisFactory()->isAvailable();
+		return \OC::$server->get('RedisFactory')->isAvailable();
 	}
 
 	protected function evalLua(string $scriptName, array $keys, array $args) {