DOC: fix documentation for copyright and credits (GH-5706)

DOC: fix documentation for copyright and credits (GH-5706)

Adapt documentation for `copyright` and `credits` to reality.  Previously, the documentation implied that all each of `copyright`,
`credits`, and `license`, would print a message to call the object in order to see the full text.  In reality, only `license` exhibits this
behaviour, and `copyright` and `credit` print their full text either when printed, displayed, or called.
(cherry picked from commit 243d6d71265be1996a8326002deae429106a5fba)

Co-authored-by: Gerrit Holl <gerrit.holl@gmail.com>