doc: Revert "doc: Add more known-warnings"

This reverts commit 3127d7b54c22449fcc85dd1c59ca294885d5f997 which
was forgotten when switching back to breathe from docleaf and  causing
unecessary "here's a warning about something that's not actually
a warning" :)

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>
1 file changed