Very minor spelling/phrasing suggestions for docs

[MareikeJaniak]

Some very minor suggestions for spelling/phrasing.

• The word "Centre" is spelled in the American way in at least one place, while it is "Centre" in most other places: https://genpipes.readthedocs.io/en/genpipes-v4.4.1/index.html#genpipes-genpipes-version-documentation (In the note box)
• In the section "Introducing GenPipes" there is a heading labelled "How GenPipes works?" (https://genpipes.readthedocs.io/en/genpipes-v4.4.1/get-started/what_is_genpipes.html?highlight=how%20genpipes%20works%3F#how-genpipes-works). I would suggest either dropping the question mark or rephrasing it into an actual question: "How does GenPipes work?"