Optimal captain choice -small fix on enum :)

Hey, 
I was trying out the Optimal captain choice example but the enum is not working since its not picking the values from the dictionary:

Old code: 
```
 for i, elements in enumerate(picks):
            gameweek = i + 1
```

Fix:
```
 for i, elements in enumerate(picks.values()):
            gameweek = i + 1
```