Minor docs typo fixes
# What does this PR do?
Just a few typo fixes in the docs.

## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).

## Who can review?
@sgugger
Looks like you have a styling problem, could you run the command `make style` after doing a dev install with
```
pip install -e .[dev]
```
in the repo?<|||||>Oops! Done.