Standardize spacing in explanation.txt

As of this writing, we have the block of text in the explanation for `intro init`
```
The ".git" folder contains a lot of information that Git can use to help you
manage different versions of your code. You don't ever need to do anything with
the contents of the ".git" folder directly
```

We manually changed the spacing, but once we implement word wrap with #274 , we will want every line of every `explanation.txt` to just be one long line.

Like this:
```
The ".git" folder contains a lot of information that Git can use to help you manage different versions of your code. You don't ever need to do anything with the contents of the ".git" folder directly
```