doc: the typo train

Context

This is the current edition of the typo train, an MR batching together small and non-controversial changes to the documentation. Feel free to contribute with commits, under the following rules:

• As long as in Draft mode, the train is open to new commits, and closed for reviews.
• Once marked Ready, the train is closed to new commits, and open to reviews.

Enjoy active reading of the doc.

The last edition of the typo train was !3687 (merged).

Manually testing the MR

Checklist

• Select suitable reviewers using the Reviewers field below.