doc: fix doxygen warning
doc: fix doxygen warning

This fixes the following warning:

warning: argument 'a4wide' for option PAPER_TYPE is not a valid enum value
Using the default: a4!

Signed-off-by: Alexander Stein <dbef83f64948dc68aad31596bbf6991154a9d730@mailbox.org>
Signed-off-by: Bartosz Golaszewski <e5d45fddd9040473413b909b802f629a971ad04c@baylibre.com>

brgl/libgpiod,brgl/libgpiod,brgl/libgpiod,brgl/libgpiod