fix typos in docs

[noviluni]

Hi! I fixed some typos, if you want to keep something as-is for "historical reasons" just tell me or commit.

Thanks in advance!

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• Target the master branch for bug fixes, documentation updates and trivial changes.
• Target the features branch for new features, improvements, and removals/deprecations.
• Include documentation when adding new features.
• Include new tests or update existing tests when applicable.

[nicoddemus]

Thanks @noviluni!