Remove one-line syntax & implicit subject

[Rachel Moser]

Suggestion made by programmurr, for Lesson 2:

I suggest removing the one-line syntax. I didn't know it existed until I saw this ha! That's great, I learned something new, but I think for beginning beginners (unlike experienced beginners like me lol), I think it's better just to focus on multi-line. Maybe mention one-line in a comment, but as the focus is on implicit/explicit subjects, keep the learners focused on that.

The implicit subject will come back up later on in lesson 11, but at the same time, I have even thought about removing #11 from the course too. As it is not required to use in tic-tac-toe or connect four.