Help: Remove recommendations for using CMAKE_CFG_INTDIR

Commit e71c4f7729 (CMAKE_CFG_INTDIR: Formally deprecate in favor of
$<CONFIG>, 2021-05-27) only updated the docs for CMAKE_CFG_INTDIR
itself, but other parts of the docs still used it. Update the other places
to avoid referring to the now-deprecated variable.
2 files changed