[UPDATE] An unproper description in the Prerequisites in unit1.ipynb

[Croolch]

What do you want to improve?

I suggest listing some concepts that are more relative such as RL process in the prerequisites in unit1.ipynb.

• Explain the typo/error or the part of the course you want to improve

There are no concepts explained in Unit 1 such as MC, TD. It may cause some confusions when someone read about it as a learner.

• Also, don't hesitate to open a Pull Request with the update.

#500

[simoninithomas]

Thanks for pointing this out 🤗 I merged your PR. I'm closing this issue.