Fix typo: `tha` -> `that`, remove trailing semicolons

[delirious-lettuce]

Thanks for the great blog post!

I noticed a single typo while reading your post and then found a few trailing semicolons while I was in the notebook fixing it.

[jakevdp]

Thanks! But I use trailing semicolons deliberately to suppress the output of the textual representation of the plot object. It just makes the post much cleaner.