[UPDATE] Typo in Unit 1

[RichardKhanhWin]

There is a typo on this line in Unit 1:
Reward function (the function that will gives a reward at each timestep) 💰:

It should be:
Reward function (the function that will give a reward at each timestep) 💰:

[simoninithomas]

Hey, thanks for pointing this out 🤗 I merged the PR thanks