Fix typo in beforeSleep() comment.

src/redis.c

@@ -1258,7 +1258,7 @@ void beforeSleep(struct aeEventLoop *eventLoop) {
     REDIS_NOTUSED(eventLoop);
 
     /* Call the Redis Cluster before sleep function. Note that this function
-     * may change the state of Redis Cluster (frok ok to fail or vice versa),
+     * may change the state of Redis Cluster (from ok to fail or vice versa),
      * so it's a good idea to call it before serving the unblocked clients
      * later in this function. */
     if (server.cluster_enabled) clusterBeforeSleep();