doc: Document effects of ownership change on privileges

doc: Document effects of ownership change on privileges

Explicitly document that privileges are transferred along with the
ownership. Backpatch to all supported versions since this behavior
has always been present.

Author: Laurenz Albe <[email protected]>
Reviewed-by: Daniel Gustafsson <[email protected]>
Reviewed-by: David G. Johnston <[email protected]>
Reviewed-by: Tom Lane <[email protected]>
Reviewed-by: Josef Šimánek <[email protected]>
Reported-by: Gilles Parc <[email protected]>
Discussion: https://postgr.es/m/2023185982.281851219.1646733038464[email protected]
Backpatch-through: 14