update small error in example for fib function for Async.parallel

The original version had

```
let rec fib x = if x <= 2 then 1 else fib(x-1) + fib(x-2)
let fibs =
    Async.Parallel [ for i in 0..40 -> async { return fib(i) } ]
    |> Async.RunSynchronously
printfn "N^2 = %A" fibs
System.Console.ReadKey(true)
```
I changed this to

```
let rec fib x = if x < 2 then 1 else fib(x-1) + fib(x-2)

let fibs = 
    Async.Parallel [ for i in 0..40 -> async { return fib(i) } ]
    |> Async.RunSynchronously

printfn "The Fibonacci numbers are %A" fibs

System.Console.ReadKey(true)
```

to more accurately reflect the actual function.